From pages 83 and 84 of Cameras of the People's Republic of China, by Douglas St Denny, this is the first version of the Seagull 203, manufactured by the Shanghai Camera Factory, from 1964 to 1975 or thereabouts. It isn't the second version as that had an accessory shoe where the film reminder dial is on the first version, and the first has EV scale coupling which the second doesn't. Its features are listed as "Coupled rangefinder, front element focussing, coupled EV scale, film speed reminder dial, along with camera setting suggestions on top plate. Lever advance with double exposure prevention, ruby window frame counting. Built in hinged masks for 6 x 4.5 cm." It also has a metal film advance lever versus the plastic on the second version. St Denny says it is one of the most common 120 rollfilm cameras in China.
All the above thanks not only to Douglas St Denny, but also captainslack, whom I haven't seen post in a while. He was kind enough to purchase the book and send it to me. Makes fascinating reading, and once in a while a chance to sound like I know a lot about chinese cameras. I don't, but I can read. 😛