The SS1 is a 17 jewel, manual wind watch movement which was designed and manufactured by the Shanghai Watch Factory. Its design is derived from that of Shanghai's earlier A581 movement. The first variant, the SS1A, with a 18,000 bph escapement, was manufactured from 1966 to 1972, after which it was replaced by SS1K variant, which featured a 21,600 bph escapement and was manufactured until 1975. The SS1 replaced the A581 and its derived movements as the primary movement for the factory's own Shanghai brand until they began to use the Chinese Standard Movement in 1974. It was also used in many other brands.
The SS1 is derived from Shanghai's earlier A581 and A611 movements (the A611 is itself derived from the A581). The most immediately apparent change is the shape of the wheel train bridge. Unlike the A581 (but like the A611), the SS1's balance wheel has no poising screws and the balance cock features a shock-resistance spring. The mechanism for regulating the balance is different from either the A581 or A611.
The SS1 wheel train bridge is commonly stamped with "SHANGHAI" on one line and "17 ZUAN" on the line below, but several variants exist:
- SS1 movements used in HaiShi brand watches had a silhouette of a sea lion with a ball on its nose stamped in place of both the "SHANGHAI" and "17 ZUAN" lines
- SS1 movements used in JieFang brand watches had "JIEFANG" stamped in place of "SHANGHAI"
- SS1 movements used in Shancheng brand watches had "SHANCHENG" stamped in place of "SHANGHAI"
- SS1 movements used in Suzhou brand watches had "SUZHOU" stamped in place of "SHANGHAI"
Base plate markings
Most SS1s have "SS1" stamped into the base plate, underneath the balance wheel, but several variants exist.
SS1 movements have a two-character date code stamped into the base plate, underneath the balance wheel, above the "SS1" marking (or its alternative from the list above). The first character indicates the year of manufacture, with A corresponding to the 1966, B to 1967 and so on up to J, which corresponds to 1975, the final year of production. Similarly, the second character indicates the month, with A corresponding to January, B to February, and so on up to L for December. Some example codes:
- AA = January, 1966 (first month of production)
- DF = June, 1969
- HH = August, 1973
- JL = December, 1975 (final month of production)
A complete table of date codes for the SS1 and ZSH Tongji movements can be found here. The table runs from AA (January, 1966) through to JL (December, 1975). 1966 and 1975 are the first and last years of production, but the first and last months of production within those years are unknown, so, for example, AA and JL marked movements may not exist.
Some SS1 movements have additional markings stamped into the base plate, underneath the balance wheel, on a deeper part of the plate to the left of the movement identifier and date code.
- Haiou brand watches are sometimes stamped with "HO"
Watch brands using the SS1
- Shanghai (model numbers below)
- 1010 (SS1)
- 1020 (SS1)
- 1110 (SS1)
- 1120 (SS1)
- 1123 (SS1)
- 1523 (SS1, SS1-K)
- 1524 (SS1, SS1-K)
- Watchuseek forum thread: Shanghai SS1 & SS7/ZSH/ZSE production date codes - Torsten & gigfy
- Watchuseek forum thread: An SS1 tear down...
- Watchuseek forum thread: Shanghai 1120 maintenance.....