Canon 13mm C16 lens – elements good but the focus is too free & feels like it isn’t making contact or rotating anything. Aperture works fine but the front will readily screw out. Slight ding in front of lens shade as you can see. The black edging on the front is spotty too – see pics. Great if you are handy to pull it to bits to overhaul it. Sold as is. Pls check out my other items, you won't believe the variety. No ideas on the mount but had to tick something thanks to ebay's automated crap otherwise it wouldn't list