Looks to me like the rear seams for the outer sills have been filled over. Is it just my computer?
https://cgi.ebay.com/ebaymotors/Triumph-TR3-1959-roadster-restored-/300783995211?forcev4exp=true
https://cgi.ebay.com/ebaymotors/Triumph-TR3-1959-roadster-restored-/300783995211?forcev4exp=true