Mk I, Mk II, and the cosmetics

McIntosh Laboratory — McIntosh run letters (D/G) mark production runs, and chassis revision can lag

MC240 / MC275 era · 3 rows · confidence Medium · AudioKarma forum — thread mc240 production information request

Resolver: when a number and a chassis revision disagree, the answer is the range, not a corrected number: units were built in batches from pre-made sub-assemblies, so a number of one era can sit on a chassis of the next.

Marantz — Marantz two-digit serial prefix (year + six-week period) that replaced the stamp

1960s-1980 (AMK's own wording: 'we believe') · 5 rows · confidence Low · AMK Products — Marantz production numbers

Two traps the source flags: the prefix reading is AMK's interpretation ('we believe'), not a Marantz publication; and the region letter is not a date - a European unit can look 'later' than a US unit of the same era because European serials started at 50001 for some models.

Quad (Acoustical Manufacturing) — Quad II era features by serial-number threshold

1953-1971 (Quad II built 1953-1970/71, 90,000 domestic units) · 7 rows · confidence Medium · Keith Snook — Quad II restoration research

Physical features, not a code: they identify the GENERATION of a chassis, and they are exactly what restorers swap. The source warns that transformers and nameplates are trivially interchangeable, so the age of a Quad II has to be assembled from three or more features (serial + plate type + bush/screw type + can cosmetics).

Thorens — TD-124 Mk I -> Mk II changeover at about 59,000

spring 1965 · 4 rows · confidence Medium · RetroTone (UK) — Thorens TD-124 dating research

Mk I was sold to about spring 1965 and Mk II to about the end of 1967, but dealers carried stock for years afterwards.

Revox (Willi Studer) — A77 Mark I-IV: serial brackets, dates and the features that prove each Mark

1967-1977 · 7 rows · confidence High · ReelToReel.nl — Studer/Revox QRG documents (PDF)

The S/G prefix is the place of assembly, NOT a version - a common mis-reading. Community cross-check: a restoration guide dates Mk I 1967-69, Mk II 1969-71, Mk III 1971-73, Mk IV 1973-77, which agrees with the QRG to the year.

Dynaco — Dynaco serial-number formula (product code + year + week + unit within week)

1957-1970s · 7 rows · confidence Low · GeoCities mirror (community archive)

The first digit has to be read as a product code - taking it as a year is the classic mis-read.

Fisher Radio (The Fisher) — Fisher: documented serial ranges per chassis come from the manuals

1950s-1969 · 4 rows · confidence Medium · Fisher Consoles — Fisher console & receiver archive

Identifies the version or the era from physical features, so the table narrows the period rather than pinning a year.

Garrard Engineering — Garrard 401 version features

1964-1977 · 4 rows · confidence Medium · Gramophone Music — Garrard service notes

Feature/era identification. Production-count conflict recorded, not averaged: Gramophone Music says approximately 74,000 units had been sold by 1977, Artisan Fidelity says 'some 50,000 plus units' during a 12-year run.

Dual (Gebrüder Steidinger) — Where a Dual's serial number physically is, by era (and why it goes missing)

1907-1980s · 7 rows · confidence Medium · Dual-Board (DE) — Dual collector forum

Practical identification: it says where to look for the era of the machine, and explains the common case 'my Dual has no number'. An American thread documents the same sticker-under-the-platter location for the 1219/1229 and notes it is frequently lost; another notes that on the 1219 the platter has to come off because the mat is glued on.

Heath Company (Heathkit) — Heathkit company eras and catalogue size by year

1947-2012 · 7 rows · confidence Medium · Ohio University — vintage electronics archives

Era context for dating a Heathkit by its catalogue appearance or model list - the catalogue counts are quoted as printed by the article, and it notes its own 1987 count of 221 'with some of those being modules for other kits'.

Accuphase Laboratory — Kensonic Laboratory to Accuphase Laboratory - company eras, not brand eras

1972-1982 (company name) against 1972-present (brand) · 4 rows · confidence High · Accuphase — official product museum & service pages (PDF)

Correction of a common collector claim: there is no 'Kensonic-badged era' of Accuphase products. Kensonic is the company that made Accuphase-badged units from the first model. Only the legal name changed, in 1982.

Luxman — Luxman valve line markers: SQ, MQ, CL, MA

1958-1970s, with the CL/MQ letters still in use today · 6 rows · confidence High · www.luxman.com

A valve Luxman is identified by its letters before any date: SQ (integrated), MQ (power), CL (control unit / preamp), MA (early power unit). The same letters on a modern unit mean the reissue line, not a vintage build - the model number, not the prefix, decides.

Yamaha (Hi-Fi) — Yamaha integrated amplifier generations (official history)

1972-1990 · 12 rows · confidence High · ca.yamaha.com

Generations are witnessed by the model number plus the switch: CA-1000 family (1973-1976), CA-2000 (1976), A-series from 1977, and from 1983 a Class A unit with no switch at all. A 'CA-' number on the faceplate therefore means 1972-1976, never later.

Sansui Electric — Sansui serial number: the year digit position (rule only, not a range table)

1960s-1980s · 2 rows · confidence Medium · Sansui.us — collector reference (production-date rule)

The source itself warns that the year code is the production year of the unit, not the introduction year of the model.

J.E. Sugden & Sons — Sugden A21 variants: Richard Allan badge, Series 2/3, A21a, A21SE, Signature

1967-2015 · 9 rows · confidence High · Sugden — official ampography

The Richard Allan badge is the trap: those units are 1967-1968 Sugden builds sold under another maker's name, and they are the earliest A21s. A 'Sugden' faceplate therefore means 1969 or later. The A21 has been in production for nearly sixty years, so the suffix (Series 2/3, a, a Series 2, SE, Signature) carries the whole date.

Musical Fidelity — Musical Fidelity product landmarks (official timeline)

1982-2012 · 10 rows · confidence High · Musical Fidelity — official support

Landmarks date a FAMILY: an A370 cannot be earlier than 1986 and an X-10D cannot be earlier than 1995. They do not date a unit, and the timeline is explicitly 'a small selection' of products, so absence from it proves nothing.