A-body Rim-Blow wheel

They aren't super common. Although, I wouldn't say they're really rare either. Especially for '71 cars, the factory seemed to throw them on everything (last year of the rim blow wheel). My EL5 GT has one, I would suspect my other GT had one as well as it was among the items missing from the car that the last jerk of a PO pulled for his car.

Biggest issue with them is that the plastic cracks, so if you find an original it usually has to be restored. And even if the plastic isn't cracked, the rim blow function can be pretty hit and miss.

They are being re-popped, I've seen them on eBay for a pretty reasonable price considering what it costs to have them restored.