What is the correct snare frame for a COB Dynasonic ser. #42743. From the posts on the Rogers Owners Forum I think that's around 1974 (please correct me). The botton rim is a 3 piece version, but snare frame is the blunt end type associated with the "Big R" drum.

Is it possible that this was a transitional drum, built with the last of the 3 piece rims and the first of the blunt end frames? Or, do I really need a 4th version ladder type frame to make the drum period correct?

Thanks