Dad had several ‘56 Crown Vic’s, a few 57 T-birds, and some 49-54 Merc’s. I suspect this may be a 56, but not sure.
NOT tri-five Chevy, there is a full frame at Eckler's doesn't match. Those latches didn't match up with anything I saw for 50s fords. https://www.ecosia.org/images?q=1956 ford convertible top latch I tried 40s and 50s. Didn't see anything to match https://www.ecosia.org/images?q=1940s+convertible+top+latch These 60s Chrysler latches have the wide rectangular handle, but not the raised area. https://www.legendaryautointeriors.com/products/ct65abc-latch Most Ford and GM seem to have a fairly narrow handle. Designers will change things up, of course, but I didn't see that flat, wide handle in their lines.
The partnumber shown on one photo is NOT typical of a Ford/Mercury part number. Post WW2 would have a prefix "0A", "9A" "B5A" "B7Ax" (1950 Ford, 1950 Mercury, 1955 Ford, 1957 Ford something) and a body of the number similar to 76xxxxx, 76 being a convertible. B5A 76123456 might be the format.
Bump for more eyes. I know a bare convert frame isn't the easiest to ID by picture, but the power of the HAMB should get this one.
It’s off a Dodge . Honestly , I would guess European car by the shape and “ daintiness” of the frame .