It looks like all three chassis use the same chassis forms with tube sockets and IF transformers all in the same places. If so, then Midland probably used the same cabinets for all three chassis. Two model numbers for each chassis would indicate two different cabinet styles -- either one wood and one plastic (Bakelite), or one brown plastic and one white plastic.
:I have just acquired a 1946 Midland tabletop radio but can't seem to locate a model number for it. The Midland model M6B looks alot like it but mine has 6 tubes while the M6B has only 5. Can you help?