L3 on both caseback & movement. Notice the pitched Dauphine hands, with matching Dauphine seconds hand. The amount of wabi on this watch was phenomenal, and took 3 hours to remove, but on the upside it protected the bezel and upper surfaces from wear and they are in very good condition. Unfortunately, the caseback has a little hole and bad plate wear. The movement is in good order apart from the hairspring being bent, stopping it from working.

1959 (L9) case with a 17 Jewel 11AF movement dated M0 for 1960. Very similar to the 1948 Brewster as seen in the attached photos. I'm not suggesting its a 1960 Brewster...I'm just pointing out it's exactly the same size and shape with minor differences such as the lugs and on the bezel at the crown. It will help in identification i think. 

II have two of these similar watch cases and bezels and three different movements and case backs. The subject watch  question is the first photo - a 1948 dated case with a 1947 dated 15J 10BC movement. In the second photo I show both my complete watches (L: 1948 Brewster; R: 1960 Unknown; Middle: 1946 dated 15J 10BC with a case back that starts with a "5" for 1945. The case back fits the Brewster bezel. The third watch on the right is a 1959 (L9) dated case with a 1960 (M0) date 17J 11AF movement. The third photo shows the this subject watch in comparison to the 1960 dated 11AF watch. The bezel is only slightly different in the lugs and in the crown area - otherwise they are exactly the same size and take the same crystal. I could not find any similar bezel and case for 1959-60 so I'll post it as an Unknown...however, I did want to point out the similarities between the two watches. 

Case measures 41.5mm lug to lug x 21mm non inclusive of the Crown using Calipers. Ribbed Dial shows Black printed Hour markers, Bulova signature and Seconds register, the Dial is absent of a Minutes register. Hour and Minute Hands are Black Alpha style and a Black Index style Seconds Hand appears on a sub Dial fully obscuring the 6. Crown is signed. Caseback is Gold and stamped as shown. 

Movement is stamped  J9 Nice two tone dial and gold gilt hands and raised gold numbers. Keeping excellent time sweet find....