I have an ongoing project where I put odd lenses and other contraptions in front of my SLRs, and in connection with that project I have long wanted to put my hands on some M42 lenses – lenses with a 42mm thread rather than a bayonet style lens mount. The M42 standard has its roots in eastern Europe, and was originally introduced by Contax in 1949, and was adapted by a lot of manufacturers like Praktica, Pentax, Ricoh, Zenit and many more.
Today it's not used any more, and according to my knowledge there are no lenses produced with 42mm thread these days.
They are widely available used, and I found a Russian Industar 50mm f/3.5, which was just what I was looking for for my project. The lens was in Ukraine, and considering the current state of that country, ordering it could seem a bit risky. But I have ordered stuff from Ukraine before, and at app. 30 US$ I thought it was worth trying.
The purchase was confirmed, and I even got a track&trace number for the package, which arrived a few days ago – from Mariupol of all places, right up against the conflict area in eastern Ukraine. I watched the news the same evening, and Mariupol was mentioned several times together with words like gunfire, shelling, granades and Russian troops.
But Mariupol obviously also has businesses running and a working post office, and I got my lens and am now fooling around with this crude, cold war, Russian piece of glass on my state of the art digital SLRs.