According to "Soviet" aka "Zhang" a former Watchuseek moderator and collector living in Beijing, a "total of only some 160,000 BS-2 were made between 1961-1968 for all the versions".
Also, some historians note that many of these were returned to Beijing Watch Factory in a trade-in deal, of which Chinese Watch Wiki states: "Many of them were destroyed in 1987 and 1988 when the factory accepted them as trade-ins for newer models"
I found a Sohu.com article with this Google translated history regarding the genealogy of the movement:
"Leobe is a watch brand registered by Cervine SA in Switzerland on July 10, 1946 in La Chaux-de-Fonds, Switzerland. In 1960, Peng Zhen, the mayor of Beijing, contacted the Swiss Labor Party, and spent 1.75 million to buy its watch movement equipment and drawings from Switzerland as a whole, and distributed the equipment to Beijing, Nanjing, and Guangzhou watch factories (see Xu Yaonan's memoirs). The Beijing Watch Factory has since developed the Type II (BS-2) watch and started production in 1961. The initial production of the second-type [BS2] watch was 17 diamonds."
(More on the legendary Xu Yaonan here: http://en.beijingwatch.com/watchmaker/35. )
I have a second BS2, also 18 jewels--but the crown and stem are not original. Given the rarity, I'm still pleased to have it, and knew of the issue when I bought it as the seller disclosed the problem.
The other items in the top photo are a USB key/souvenir card from my 2014 visit to Beijing Watch Factory, and a Beijing Watch factory pin I received when I visited BJWAF's flagship store in Beijing in 2019.
The souvenir card features a photo of BJWAF's "Playing Dragon and Phoenix" tourbillon, built under Mr. Xu Yaonan's technical direction.
More photos of the "Playing Dragon and Phoenix"and a 2018 meeting with Mr. Liu Dong, the Master Engraver whose work is featured on the watch, here: https://www.amchpr.com/beijingmay.html
Curator: Alberta Museum of Chinese Horology in Peace River; Member: China Horologe Association; Chief Expert: China Watch Overseas Working Committee (CWOWC); Sino-Canadian Horological Cultural Affairs...