17 jewels = original Venus 175
19 jewels = original 1960's Chinese military chronograph (project 304)
21 jewels = ST1901 from Tsinlien Sea-Gull
23 jewels = ST1901 from Sea-Gull branded watches
There have been many, many variants of these watches. All I can do is speculate, but since these are made in batches and from what appears to be different sources in HK there are (and will continue to be) different variants.
This is what I can piece together:
- jtbold sourced the first batch (19 zuan, unfilled star, solid back).
- Then cnmark sourced multiple batches (and noted differences in every batch). His first batch was like jtbolds, then his second & subsequent batches started having small differences (filled stars, swapped register hands, glass back option).
- Then WatchUnique (and a few other Northern European sellers) offered the 21zuan in different variants (21zuan dials, etc.). And a few of those sellers re-branded them with their own brands (sorry I can't recall the names).
- Now Thomas is offering single watches hand assembled from his stock (signed crowns, dial errors, etc.). Which I think will continue to increase the variants.
BTW, mine from cnmark's second batch also has the register hands swapped.
(click on pics)
Here is one from jtbold's batch (that I purchased and traded to a very nice guy from Gibraltar for a cnmark first batch 0437)