Rare Baoshihua SZ1 prototype (1st issued STD Mov'mt, made before 1974)

The attached is the pie-pan Baoshihua with “SZ1” movement. This movement has smaller balance wheel than the later SZE movement and has a special "click" system. The code under the balance wheel; upper is 2GG, bottom is SZ1. I personal think that this is the prototype.