The Ford Mustang was available from day one with a retractable soft top convertible roof, offering buyers the option of open-air fun at the push of a button. Ford also toyed with the idea of adding a retractable hardtop option to the first-generation Mustang, just as it had offered on earlier Ford Fairlane 500 Skyliner models. Ultimately, the Blue Oval decided the option wouldn’t be popular enough at an acceptable price point, leaving the aftermarket to take care of the few customers that just had to have a retractable metal roof.

One of the few first-gen Mustangs to ever have a convertible hardtop conversion done is heading to auction soon, reports Hemmings Auto Blog, though what’ll bring when the gavel comes down is a question better left to someone else.

What we can tell you is that the man behind this hardtop convertible conversion, Ben Smith, originally pitched the idea to Ford itself. Ford passed though, and it wouldn’t be until the 1990s that Smith would get another chance to make his concept become a reality. Ben himself built 3 such retractable hardtop conversion prototypes, possibly including the car going to auction, though there seems to some confusion on the issue.

That’s ultimately the problem with such aftermarket conversions though, as it can be hard to affirm anything without all the right paperwork. What’s more, the low take-rate of the conversion seemed to confirm Ford’s misgivings, that the extra cost wasn’t worth the retooling and research. It’s a cool idea, but one that ultimately remains little more than a footnote in the Mustang’s long history. How much value can a footnote possibly hold?