Well I'll give it a try, but I'm not have much luck coming up with former Jinan model numbers. In fact, so far I have only been able to find one, JN150, which is the model number of the famous Huanghe truck of 1960. The puzzle picture doesn't look anything like those I've seen of the Huanghe, although I suppose it could be some sort of prototype or variant. Rather, since the puzzle vehicle is earlier (1958 vs 1960), I would guess that it carries a model number beginning with the letters JN, and having a number lower than 150. Am I even close to being on the correct path?