Since there is no official document has left from former Shanghai Watch Factory, the only reliable and available document is the record from the Shanghai City Government website about their light industry history. http://www.shtong.gov.cn/node2/node2245/node68930/node68935/node68960/node68972/userobject1ai66697.html
I have translated a small paragraph here, I think it may good for Chinese vintage watch collectors to share.
Quote..
“From 1965 onward, Shanghai Watch Industry had invented and developed, model 591 automatic movement watch, model 611, 631, 657 mid-size men watch and the high grade A641 24J mechanical men watch. The movement power-reserve had increase to 45hrs from 40hrs since model SS1A had launched. The 1st million production was in 1968 and had increase to 2.28 million on 1970. The factory had also produced SSI/1 mid-size men watch, SS4, SS4H-K 19J mechanical men watch, SS4B 19J calendar men watch, SS2C 29J automatic men watch, SS4C 24J automatic calendar men watch, SS6P automatic calendar men watch & SS2B 29 automatic calendar watch, etc. On 1972, SSI had enhanced to SSIK high beat movement from 18000 bph increased to 21600 bph; daily average error had improved from 45s/day to 30s/day and it also reached the National 1st grade standard.”
