Body first: TUCKER has already stated that the body is the remains of #55. The inner rear wheelwells (SuperFleye's indre hjulhus) look like more rust than metal at the time of these photos. So the damage adds up. TUCKER, have you got some higher resolution pix of the following photos of #55 (or other photos) to help finish off the body piece of the puzzle:


Frame: There's also that frame from #55 that still looks to be pretty good at this point. The rear part of the frame is missing, unless that's it sticking out the rear window...
As far as the test frame goes, it's baffling. The LIFE photos prove that "Test Chassis #2" cannot be #52 from the welding production line. However, Lot #684 was described as being "Test Chassis #2" with the cowl from #52. #52's cowl must therefore have been added after the 1950 auction, unless the frame is also #52. But then the test chassis would be missing. What better way to hide the original "Test Chassis #2" than to call Lot #684 the test chassis, as nobody would look elsewhere for the test frame?
Even if Lot #684 did include the original test chassis (then where is frame #52?), Phil Egan made it clear that there were several more test chassis made "to contain" the drivetrain developments that were ongoing (has anyone ever looked at Gene Haustein's photos?):

It's only a matter of time and research until the actual records, blueprints, or closeup photos of the various test chassis are found that describe exactly how each of them were made (assuming the frame really was Tucker-built). FYI, here's a list of the specs for the various gauge steel thicknesses:

