I contacted a.y.a.regarding my sxs a.y.a.the gun number starts 16xxxx and the only information they gave me was made in 1963 and the model is 400 e./my shotgun is a 12bore witch has 28inch barrels,ejectors,straight hand stock with brass oval inlay,double triggers,on the action I have 2screws and 2 pins but no locking screws, on the action there is some engraving exactly like the picture of your gun,on the front lump there is a extractor retaining pin/screw.i have been informed by my local gun shop/dealer that my gun is not a a.y.a no4 because it has not got locking screws on the action,(that is the only difference between my shotgun and a proper a.y.a no 4) and should Not be sold as a no 4.hope this information helps you out. I think it would pay you to e.mail a.y.a to find out what they say,they replied back to me within a hour,hope this info helps you.WELSH GROUSE.