It looks like a Westfield (Columbia) frame. They built most Elgins til 37 or so, then Murray built most, thru the JC Higgins era. Not entirely though, I have seen other Westfield JCH's, but not many! Should be 3 things stamped on the BB. "MOD 502", then a 4 or 5 digit #, then another # under that. I can tell the year fairly close by that 2nd #, which is the catalog #. -Adam