In 1971, I bought a 69 280SL with only a soft top; no idea of its history, just how it came. My friend, who had a wrecking yard, got in a wrecked '71 with a red hardtop in perfect condition, so...; the fact that my car was beige with a dark brown tex interior meant that the match wasn't great but that mattered little in the nasty PA winters! In those days, a hardtop would bring $4-600 and there was a ready market. Keep in mind that these cars have been around for 50 years or so and that many have been wrecked and/or parted out, cars and hardtops have been stolen and in some cases, just sold without the hardtop for whatever reason. The idea of a hardtop "registry" is a good one IMHO for reuniting them with cars and for identifying ones that may have been stolen.