I'll need to look at mine more carefully for comparison. Serial # AE 852940 gives a date of 1938 and Model 15 according to ISMAACS. Then I have the same 15-80 bobbin assembly as SewAnnie's. Is there a site showing the more subtle differences by year and factory that gives the rest of the model number designation as 15- whatever? Were the RAF decals only made in England and Scotland? Wish I could find my camera. I love seeing another RAF and the collaborative sleuthing that is going on here.