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Reference Library · Patent Dossier

Federal Products — Providence
C. C. Street & the Miracle Movement

The Providence chapter: Street's conjugate crown-gear patent behind Federal's test indicators, and the documentation frame for the Miracle Movement — the collection's founding brand. REV D: "Testmaster" is established as a badge applied across multiple outside manufacturers. "Federal" stops meaning "made by Federal."

Doc No.REF-PAT-FED

RevD · 2026-07-11

FamilyDTI · conjugate crown gear / plunger · Miracle Movement

StatusUS 2,141,627 verified · Testmaster = multi-supplier BADGE · Miracle Movement OPEN

Unmarked claims are Established (primary source or physical unit) Open unresolved, with the method that would settle it

01 · Lineage

Providence: the design-house gauge maker

Federal Products Corporation of Providence, Rhode Island grew up in Brown & Sharpe's hometown and became the other serious American indicator house — arguably the most design-conscious of them. Chauncey C. Street was Federal's house inventor; his 1937 filing shows the firm's engineering temperament exactly: rather than accept the compromises every other maker lived with, Federal invented a new gear tooth. The corporate line runs forward to Mahr Federal — making the Puppitast on this bench a distant corporate cousin of the 1938 patent.

1937

Aug 5 — Street files the conjugate crown-gear indicator patent (Ser. 157,520), assigned to Federal Products Corporation.

1938

Dec 27 — US 2,141,627 grants. Contemporary examples exist marked "Model #One" with the patent number and no brand name — the earliest marked production tier. Note the timing: Gladwin's second patent granted June 1938, Pearson files 1941 — the late-'30s American test-indicator design race.

1940s–60s

The Miracle Movement era on the plunger dial indicator line: dials marked "FULL JEWELED" + "MIRACLE MOVEMENT," Providence R.I. Field reputation: an exceptionally good, nearly shock-proof movement. Early dial tell reported in the market: light-green ("uranium"-style) dial backgrounds on older units. Introduction date of the branding: not yet established.

era-spanning

Model-code system (plunger line): leading letter tracks dial size (A/B/C/D/E observed ascending; O-prefix metric units exist, e.g. O61 at 0.01mm), with following digits encoding graduation/range — full decode pending against collection population. Some listings show trailing codes (e.g. "72-12") that may be date codes — hypothesis to test.

1955

US 2,141,627 expires (Dec 27). Later corporate history: Federal eventually merges into Mahr Federal — the Providence line joins the German house.

1949→2005

Citation afterlife: the conjugate-tooth geometry outlived the instrument — cited by National Broach & Machine (1949), General Motors gearing patents (1966, 1975), and tapered-gear filings into the 2000s. Street's tooth math entered general mechanical engineering.

02 · Patent Record

Street's verified patent — the trail is open

One Street/Federal patent is verified below. Street was a serial inventor and Federal's portfolio is certainly larger — including whatever covers the Miracle Movement. Count stated as known, not exhaustive; the trail continues in the next research session and against patent numbers found stamped on collection units.

US 2,141,627 · VERIFIED 1 OF ?

"Gauge or Indicator" — the conjugate crown gear

InventorChauncey C. Street, Providence RI

AssigneeFederal Products Corp.

FiledAug 5, 1937 · Ser. 157,520

GrantedDec 27, 1938 · exp. Dec 27, 1955

The problem it solves

A lever test indicator wants the dial facing the operator while the stylus swings in a perpendicular plane — motion must turn a corner. At watch scale, Street states flatly, commercial bevel gears are only approximations and spiral gears are accurate only at impractical cost, with friction that forbids high magnification.

What Street invented

A crown gear whose teeth are the mathematical conjugate of an involute spur pinion: tooth flank pressure angle calculated incrementally at every radius (the formulas are in the patent), so inner and outer ends of each radial tooth — which travel at different speeds — both transmit velocity exactly. Flanks come out subtly concave; teeth taper wider at the gear's inner edge.
Continuity ≥ 1 (1.4 found satisfactory): some tooth pair is always in contact — no hand-off backlash, contact walking across the flank as a travelling line.
Manufacturing method included: the cutter is shaped as the pinion and both rotate in mesh during cutting — the gear is literally formed by its own mate's motion. Street's vivid description: visualize soft teeth shaped by the impression of the turning pinion.
The indicator embodiment is a complete DTI architecture: two-part stylus lever held by friction spring (angle adjustment), spring-bias reversal selected by an external handle (a reversing lever), gear segment → pinion → crown-gear segment → dial-staff pinion, with the dial movement as a self-contained unit.

Collector significance: the taxonomy's fifth mechanism — where Lowe used a sliding helix and Gladwin dual arms, Federal chose true gearing and had to invent the gear to get it. Earliest tier: unbranded "Model #One" units carrying this number. Multiple units bearing 2,141,627 are held in this collection — the marking-progression population for dating work. The patent number on a unit brackets production no earlier than Dec 1938; surrounding markings (brand form, additional patent numbers, dial style) do the finer dating.

Documents

Original PDF (USPTO scan) Google Patents page (full text incl. tooth formulas)

US 2,141,627 drawing sheet: DTI section, crown gear tooth projections, pinion tooth section, pressure-angle constructions — US 2,141,627 · Drawing sheet (hotlinked from Google Patents — requires internet)

03 · The Miracle Movement — documentation target

What is attested, what is open

Attested: "Miracle Movement" is Federal's branded movement for the plunger dial indicator line (models across A/B/C/D/E and metric O prefixes), marked on the dial face and typically paired with "FULL JEWELED." Field reputation records an exceptionally good, nearly shock-proof movement — the marketing name earned its keep. A known service weakness is also on record: a soft-steel component that deforms and produces stickiness (per Long Island Indicator, referenced in forum discussion) — a repair-bench detail to verify at teardown.

Open — the core questions this dossier exists to close: the patent number(s) covering the movement; the introduction date of the branding; the exact mechanism that justified the name (shock-protection architecture, gear-train arrangement, jeweling scheme); and whether Street or another Federal engineer designed it. Relationship to US 2,141,627: sibling product lines, not sequential designs — 2,141,627 is the test-indicator (lever) patent; the Miracle Movement brands the plunger line. Whether the branding pre- or post-dates 1938 is unestablished; any Miracle-marked unit with visible patent numbers in this collection resolves it instantly.

Primary documentation plan (collection-driven): (1) census all Federal units — model code, every marking, patent numbers verbatim, dial style incl. green-background early tell, "Model #One"-era unbranded features; (2) transcribe patent numbers from Miracle-marked units → pull those patents; (3) one teardown of a duplicate Miracle Movement unit, photographed and filmed to bench standard — likely the first published look inside; (4) test the "72-12"-style trailing code = date code hypothesis against the census. The collection is the archive; the record barely exists elsewhere.

03b · Ephemera Register

Collection-held factory documents

Document	Date	What it establishes
Form A-712 — Testmaster Series 80 contact point instruction sheet (original held)	© 1980	Federal's street address: 1144 Eddy Street, Providence RI 02901 (the Eddy St. plant — address + ZIP date-consistent with the 1980 copyright). Full Series 80 model decode: T = 1⅜"/35mm dial, LT = 2"/51mm dial; -82…-86 inch line, -87…-89 metric line; three contact-point length tiers per system. PT-500…PT-521 part-number block for points. Service rule set: lengths never interchangeable across tiers; metric points are blackened and differ slightly in length from inch (.541/.514, .811/.799, 1.622/1.598) — a blackened loose point is metric by definition, and a mismatched point fits but mis-measures. Digitized in full: federal-testmaster-contact-points.json.

The Testmaster Series 80 sheet also refines the model map: the Testmaster (lever DTI) line and the Miracle Movement (plunger) line carry separate numbering systems — T/LT-8x vs the letter-digit plunger codes (B21, C81…). Any Series 80 units in the collection census should be checked against this sheet's part numbers for point correctness — a cheap authenticity/completeness check the market never performs.

03c · Federal Green

The dial color — official name, no official number

Attested: Mahr's catalog designation is "soft-green tint" (inch dials); retailers carry it as Face Color: Soft Green. The tint is functional twice over — catalog copy states soft-tinted dials minimize eye strain, and the color encodes the measurement system: green = inch, soft-yellow = metric ("light green to be easy on the eyes and inch recognition," per current product copy). Same house instinct as the blackened metric Series 80 contact points (form A-712): Federal/Mahr color-codes inch vs. metric across faces and parts. The green is a continuous house signature from the early light-green ("uranium"-style) Miracle Movement-era dials through today's MarCators — surviving the Mahr merger intact.

No standard designation exists in any published record — no Pantone, RAL, FS 595, or paint-system number has ever been issued or measured publicly. The color has a name but no numbers.

Cross-system estimates — UNMEASURED, starting candidates only

System	Nearest candidates	Caveat
RAL Classic	6019 Pastellgrün (nearest); dial reads paler/grayer than the chip	Estimates from familiarity, not instrument measurement. Modern dial is a pale, desaturated, slightly cool green — whiter than most standard-deck greens. True match likely falls between chips; report nearest + ΔE when measured.
Pantone	pale green-tint families ~5595 C / 621 C / 5807 C
Hex (sRGB)	~#D4E2D0 – #DEE9D6 (clean modern dial)
FS 595	no close pale green; common deck greens run more saturated

Eras are distinct targets: vintage "uranium" green is yellower and slightly deeper than modern soft green, and surviving examples carry decades of aging/UV drift from as-printed — treat "Federal green" as at least two colors (possibly three) across production eras.

Measurement protocol (pending — collection rig is sufficient): dial shot straight-on under the studio panels with a gray card/white-balance target in frame; custom WB off the card; sample an unshadowed patch of the dial field clear of printing; average RGB → nearest-chip conversion per system with ΔE reported. One modern MarCator + one sample per vintage era in the census, same session and lighting = the first published numeric characterization of Federal green. Results land here as a REV increment: era / sample unit / measured sRGB / nearest RAL / nearest Pantone / ΔE.

REV D — green travels across suppliers. The collection's Swiss-built LT-150 (.00005″, an inch instrument) carries a green dial. So Federal applied its green/yellow inch/metric coding to a movement built in Switzerland, exactly as to one built in Providence. Dial colour therefore attributes nothing about who built an instrument — it is Providence's print shop, and it encodes units. Recorded explicitly, because using green as a maker tell would quietly corrupt the census.

This makes the measurement more valuable, not less: if the same green appears on an in-house plunger gauge, a Crayford lever DTI and a Swiss LT-150, then a calibrated reading becomes a cross-supplier dating instrument — one number bracketing units from three countries onto a single Federal timeline. measurement still pending

03d · The Testmaster is a Badge

Federal stopped building its own lever indicators

Street's US 2,141,627 is a horizontal-dial instrument, and it is the finest piece of engineering in this library. By the 1970s the professional default had become the slant dial — the format Interapid made standard — and Federal did not have one. They did not tool a new movement. They bought lever indicators from outside makers and printed FEDERAL on the dial. Not from one supplier. From several.

This is not speculative. It is attested by instruments in the collection and by dials in the market. Brown & Sharpe — three miles away in the same city — had already done exactly this, selling a Swiss-made instrument as the BesTest. A lever DTI is a watchmaking product; the American houses were tooled for plunger gauges and gauging systems. Buying the lever line in was the normal answer, and Federal took it.

Testmaster	Origin on dial	Builder	Basis
Street's original	Providence	Federal, in-house conjugate crown gear, horizontal dial	US 2,141,627
T-85 · .001″ slant dial	MADE IN ENGLAND	A. Capp & Son, Ltd. Crayford, Kent — helix drive	Collection specimen. Unidirectional hand travel; T-prefix is Capp's own lever-series letter; diamond bezel jimping; hand-and-hub; Federal/Esterline case. — see REF-PAT-VDT
LT-150 · .00005″	SWISS MADE	Swiss — which firm is open (Compac / Corvus / TESA-group)	Dial marking. supplier unresolved
others	?	?	ongoing — the collection does not yet hold the full set. This section will not close for some time.

The consequence, and it is large. "Federal" is a brand, not a builder. Which is which depends on the decade and the product line. Country of origin becomes a mandatory field on every Federal unit in the census, recorded verbatim, with the surface it appears on.

Federal specified the dial, whoever built the movement

The clearest evidence that these are contract manufactures to Federal's spec, not rebadged catalogue units, is the dial artwork itself — it is uniform across suppliers who would never have printed it that way themselves:

"JEWELED" / "FULL JEWELED" — American spelling, on an English-built instrument whose maker writes jewelled, and on a Swiss-built one.
The green/yellow dial coding — Federal's inch/metric system, applied to a Swiss movement (see 03c).
Renumbering into Federal's own blocks — the Crayford unit became a T-85 in the 80-series.
An unmarked body. The T-85 carries no maker's mark, no patent number, nothing. Federal paid for a casting with nothing on it. The residue of Crayford is four words of statutory origin marking and a stray T.

Hypothesis, corrected before it hardened. A tempting reading is that the model prefix encodes the supplier — T = Capp, LT = Swiss. This dossier's own model list argues against it: T-82…T-89 and LT-82…LT-89 run in parallel across the same numbers, which is far more consistent with L being a Federal variant modifier than a maker tag. And LT-150 sits outside the 80-series block entirely. Country of origin is the discriminator. The letter is not. Open: is there a T-150? Is LT-85 English or Swiss?

How to identify who built your Federal Testmaster

Non-destructive, ordered by decisiveness. This is the deliverable — the fact is a moving target, the method is not.

Read the dial for country of origin. Providence / MADE IN ENGLAND / SWISS MADE / Germany. First cut, and often decisive. Federal never manufactured outside Providence.

Deflect the stylus, both ways, and watch the hand. Sweeps the same direction regardless of stylus sense → screw-type transfer, no gear train → A. Capp & Son. Reverses with stylus sense → a gear train → somebody else. The instrument reads magnitude, not sense. Sixty seconds, nothing comes apart.

Dial angle. Horizontal → Street's in-house design. Slant → bought in. Federal never designed a slant-dial lever indicator.

Patent number. 2,141,627 → Federal's own. Absent → consistent with an OEM unit (the T-85 carries none).

Contact point. An involute tip (pear-shaped, tapered) is Capp's geometry — US 3,161,963. Federal's own instruction sheet documents it and forbids applying a correction factor below 36°.

Bezel jimping. Diamond knurling rather than straight is a Capp trait, and it survives onto OEM units. Corroborating, not decisive.

Movement plate (bezel, crystal and dial off). The diagnostic surface. Helix → Capp. Crown gear → Street. Jewelled sector & pinion → Swiss. One look answers it.

Step 2 — the hand-travel test. A Capp-built Testmaster reads magnitude, not sense.

Federal Testmaster LT-150, Swiss Made, .00005 inch, green dial, slant dial, straight-knurled bezel, spherical contact point — SPECIMEN · Federal Testmaster **LT-150** · .00005″ · **SWISS MADE** · collection. Green dial (inch coding). Slant dial. **Straight** bezel jimping. Spherical contact point. No maker's mark or patent number visible on the body.

What the specimen shows

Observed	Reading
SWISS MADE, under FEDERAL	Federal never manufactured outside Providence. Built abroad, badged in Rhode Island.
"FULL JEWELED" American spelling	Federal specified the dial artwork for a Swiss-built movement — the same tell as on the Crayford T-85. Contract manufacture to customer spec, not a rebadged catalogue unit.
Green dial · .00005″ (inch)	Federal's inch/metric colour coding applied to a Swiss movement. Dial colour attributes nothing about the builder — see 03c.
Straight bezel jimping	Not Capp. Diamond jimping is a Crayford trait and it survives onto Capp-built OEM units. Straight knurling here is a clean negative — and it means the jimping test in the decision tree works.
Spherical contact point	Not an involute tip. Consistent with a non-Capp supplier — though styli get swapped, so corroborating rather than decisive.
Bare body, no patent number	Same white-label signature as the T-85. Whoever built it, Federal paid for a casting with nothing on it.
Slant dial, flat slab body, barrel stylus clamp	The form factor is the identification lead. supplier unresolved — Compac, Corvus and TESA ended up under common ownership, so "Swiss Made" may not resolve to a single firm the way "Made in England" resolved to Crayford. Do not guess.

Outstanding on this unit — one deflection. Push the stylus each way and watch the hand. Expected: it reverses with stylus sense (a Swiss gear train). If it sweeps the same direction both ways, this is a helix drive and something very strange is going on. Then the movement plate: jewelled sector and pinion → Swiss, confirmed.

Ongoing. The collection holds the Providence line, the Crayford T-85 and the Swiss LT-150 — but not the full set, and this will be an accumulating investigation rather than a finding. Every new Testmaster is a data point. Log country of origin, model code, dial angle, hand behaviour, patent number, contact-point profile.

03e · Contact Points — the involute tip

Form A-712 (1980, 1144 Eddy Street) and the instruction sheet from the collection's Testmaster box document a contact point Federal calls the INVOLUTE TIP CONTACT POINT.

Spherical vs involute — Federal's instruction sheet, and Desmond Capp's US 3,161,963, describing the same object

Federal's instruction	What it corroborates
Correction factors .985 · .940 · .866 .766 · .643 · .500 spherical tips only	Those are cos 10° / 20° / 30° / 40° / 50° / 60°, to three places. Federal states in print that spherical-tip error is the cosine of the lever angle. Standing advice: avoid setups above 30°.
Involute tip: compensates to ≈36°; apply no correction below 36°; do not use above 36°	Capp's US 3,161,963 illustrates the stylus at 0°, 12°, 24°, 36°. Federal's shop-floor sheet reprints the patent limit exactly — and names neither Capp, nor Crayford, nor England anywhere on the page. The tapered profile holds the working-centre distance constant at 0.306″ through every tilt, so no correction is needed. The white-label runs all the way down to the paperwork.
"clutch-mounted" contact point	US 3,161,963 closes by offering its 12° ratchet "eliminated and replaced by a frictional connection." Federal shipped that alternative embodiment.

Open — and publishable. Federal has handed us both predicted curves. Spherical: deviation follows cos θ. Involute: flat to ≈36°, then breaks down. One indicator, two contact points, Grade 0 blocks, sweep the lever angle, plot both. That chart does not exist anywhere. Federal supplied the null hypothesis in 1980 and nobody ever ran the test.

Terminology. Capp says stylus; Federal says contact point. Verdict markets a pear; Federal specifies an involute tip. Same object, one workshop in Kent, four words. Federal's is arguably the correct one — Capp generates the profile by rolling a disc along a straight edge, which traces an involute, and Providence was already an involute house via Street's spur pinion. Carried into REF-ANA.

04 · Sources

Source register

USPTO full text via Google Patents: US 2,141,627 (Street/Federal Products, Providence RI; filed 1937-08-05, granted 1938-12-27; complete specification including pressure-angle derivation and claims 1–10).
Google Patents citation index — cited by National Broach & Machine 1949, GM 1966 & 1975, later gearing filings.
Hobby-Machinist forum — unbranded "Model #One" unit marked with the patent; 1938 identification.
Practical Machinist — Miracle Movement shock-proof reputation; Long Island Indicator soft-steel stickiness reference; Mahr Federal service lineage.
Market listings (multiple) — Miracle Movement marking conventions across model codes A21/B21/B81/C71/C81Q/D81S/E81/O61 etc., FULL JEWELED pairing, Providence marking, green-dial early examples, "72-12"-style trailing codes.
Collection holdings — multiple units marked 2,141,627 (census pending); substantial Federal section (founding brand of the collection).
Collection ephemera — Federal form A-712 (© 1980), Testmaster Series 80 contact point sheet: Eddy Street address, model/part decode; digitized as federal-testmaster-contact-points.json.
Mahr Federal current datasheets and retailer listings — "soft-green tint" designation, Face Color: Soft Green, green=inch / yellow=metric coding, eye-strain rationale.

Revisions

Rev	Date	Changes
C	2026-07-08	Street US 2,141,627 verified. Miracle Movement documentation frame. Ephemera register (form A-712). Federal Green: soft-green tint, inch/metric colour coding, measurement protocol specified.
D	2026-07-11	THE TESTMASTER IS A BADGE. Federal's slant-dial lever line was built by outside makers. T-85 confirmed as A. Capp & Son, Crayford, Kent (collection specimen: Made in England, unidirectional hand travel, T-prefix, diamond jimping, bare body, Esterline case) — see REF-PAT-VDT. LT-150 confirmed SWISS MADE, supplier unresolved. Country of origin made a mandatory census field. Maker-attribution decision tree published. Federal's involute tip contact point identified as Desmond Capp's US 3,161,963 geometry, with the 36° limit and the cosine correction table reprinted from Federal's own instruction sheet. Federal Green shown to travel across suppliers — dial colour cannot attribute a builder. Model-prefix-as-supplier-code hypothesis raised and rejected against this dossier's own T-8x/LT-8x parallel numbering. parts[] block added, seeding REF-ANA. Rebuilt against the shared house stylesheet.

Library

Federal Products — ProvidenceC. C. Street & the Miracle Movement