1937 Gibson Super 400

[Sleeko]

Beautiful guitars. It's refreshing to see these without the cutaway.

[wintermoon]

Me neither. Just checking. My '37 is x-braced, 25 1/2" scale, Grover Imperials. The OP's '37 is x-braced, 25 1/2" scale, Grover open-back tuners.

Some specs of L-5's and Supers in the 30s vary, I've seen a few parallel braced '37/'38 models which differs from the typical mid '39 transition as is commonly known. Maybe these were experimental or prototypes, I don't know.
Another thing is some owners had their mid 30s open back tuner guitars retrofitted w the newly offered Imperials and Kluson Sealfasts when they became available in the late 30s. Taking off a tuner might reveal the footprint and screw holes of the open backs.