In the early 1970s, the Shanghai Watch Factory produced about 30,000 military dive watches for People's Liberation Army commanders and divers. Here's an example of one of the 24 jewel "SS4 movement" original versions from Joel Chan's wonderful Micmicmor collection (there was also a 29 jewel version):

Since that time, these pieces have become prized by collectors of vintage Chinese watches although most (although not all) of the surviving watches are well used and in rough condition.

Recently, the Shanghai Watch Factory produced a small run of a commemorative re-issue (evidently far less than 30,00 pieces) using a 22 jewel 2813 movement by Dixmont Guangzhou instead of one of their own movements. This actually makes sense since, according to WUS moderator Chascomm--who has an encyclopedic knowledge of these things--the 22 jewel DG is closer to either of the original 24 or 29 jewel movements than anything the Shanghai Watch Factory currently produces since the DG 2813 has "unidirectional auto-winding and centre seconds run indirectly off the 3rd wheel".

So, after the explanation/'s my much-prized re-issue...and I'm thrilled because this watch was a true GRAIL for me :D