Little late to reply in this old topic but I couldn't find much on the internet about this lens. I bought it for 25 euros with a T mount (seller thought is was M42 so I had to buy a T2-M42 adapter). The lens is huge (42cm) but not very heavy and has 72mm filter thread. I had to remove some dust and the coating on the backside lens seems to have been damaged a little but I don't see that on the pictures. I bought this lens to make better pictures of the moon because I have a Sigma 600mm mirror lens that is too soft and a Tamron 400mm f6.9 with exakta mount for which I don't have a teleconvertor. I had a cheap Pallas 2x teleconverter for M42, making this a 1000mm lens. It's not the best converter but the only one in M42 I have at the moment... I also have a Vivitar macro focussing teleconverter with MD mount, but first need a M42 to MD mount adapter (ordered from ebay). With the Pallas converter and some cropping I already got nice results: