It is the model of the camera.

The 4A is a model of a double-lens reflex camera produced by Shanghai Seagull Camera Factory 2. It was also the highest version of the double-lens reflex camera series at that time. The production period lasted from the late 1960s to the 1980s. During this period, there were some changes in versions and processes. From some details, insiders can identify the year and version of its production.

In fact, the early Seagull 4A is basically the same as the "Shanghai Type 4". Almost all the parts are the same, except for the different trademarks (the trademark change is also for historical reasons that will not be detailed here). From the early to mid-term, it has been equipped with a tremolo. In the picture I uploaded that you saw earlier, the adjustment button on the right is all metal and made of aluminum. (In fact, you can tell the middle and late stages just by paying attention to the metal focus button on the right. This is the most obvious identification area. ) The focus knob in the mid-term was thinner than in the early stage, not as thick and heavy as in the early stage, and there was a black rubber ring on the focus knob, but the metal part was still aluminum, white aluminum color; in the later stage, it was almost replaced with plastic parts , the entire focusing button is black, and also has a rubber black rubber ring. The early ones did not have a black rubber ring.