A while back I noticed an auction on eBay for a bizarre lens that still baffles me. It was a Sigma zoom lens, I believe from the 1980s, with an M42 screw mount, but it also had an autofocus system. The autofocus mechanism was powered with AA batteries, and resembled the autofocus system for the old Canon T-80 (with a box protruding from the side of the lens), except that it was less bulbous. The autofocus was activated with a button on the side of the lens; the seller was understandably confused as well, although it was definitely an M42 lens. I don't think it sold for very much, perhaps on account of its total obscurity. It still haunts my dreams. I expect the optical quality was so-so, but the concept of an autofocus M42-mount lens seems oddly anachronistic. I believe it was something like 35-80mm, f3.5-5.6. Was it a one-off, was it in fact a recent lens made as an odd luxury item for the Voigtländer Bessaflex, or something along those lines?