I have been putting Sperzel tuners on most of my guitars for years. Usually I buy new ones, but I recently bought a used set in an auction. After receiving them, Im wondering if theyre authentic. Here are the differences I see: 1) They do NOT have USA over the "Sperzel" engraved on the back. Also the Sperzel is etched thinner and not engraved as deeply as on my other sets 2) The thumbwheel is smaller (13.43 mm or .525) as compared to my other sets (15.6mm or 0.62). The thumbwheel is about the same diameter as the tuner housing. 3) I dont have 3 pairs of differing heights, but that could be because this is a mixed set. There is only one of the longest ones and 3 medium ones. The mediums and shorts are all pretty close to the same height. 4) One of the thumbwheels has a 5 point star with a couple of concentric rings around it, rather than the center black dot as on my other sets I didn't pay a lot for these, but now Im wondering if theyre either fake or perhaps just some very old ones. Either way, I expect Ill always buy new ones in the future. Any observations are appreciated.