c. 1977–c. 198120 variants
The original hand-wound Must Tank, in a small (SM, about 20.5 × 28 mm) and a large (LM, about 23.5 × 30.5 mm) size. Caseback numbers begin with 3 for SM and 6 for LM, followed by the serial. The coloured lacquer dials (burgundy, black, blue, cream) without numerals, the tricolour frame dials and the stone dials belong mostly to this era.
No separate reference number: the caseback carries a size digit (3 = SM, 6 = LM) and a serial, seven digits in all. Collectors identify these by size, dial and movement. Auction catalogues occasionally print other numbers for manual-wind examples (81972500 and 15705 at Antiquorum); these are recorded as notes.
Faded ends mark approximate or unknown dates. Years are as stated by the cited sources.
Specs shared by all variants. Variant pages show where a variant differs.