"T2"adapter rings

When I found a "T2"ring in a camera shop, I asked if I could take it, which was generally not a problem, it's a long time since one does not see any more lenses using this mount.

A "T2" ring is made of two parts: a lens mount (Pentax, Canon, Nikon…) fixed on a ring threaded in M42x0.75.
This ring was screwed on the Soligor or Vivitar T2 lenses, according to the brand of the camera. Of course, there is no coupling. This ring is the ancestor of TX ring (beginning of coupling) and especially of the Tamron Adaptall ring, which makes it possible to preserve the coupling of the lens with the body.
If you remove the internal M42x075 ring, you obtain a mount, equipped with 3 fastening screws, which can be assembled in place of the M42x1 adapter of part of the Russian lenses (Standard "A" mount):
Peleng (Fisheye 3.5 /8mm and 2.8/17mm)
Mir 10A
Jupiter 11A
Tair 11A
Jupiter 21A
Tair 3A (and Photosniper)
500 & 1000 mirror-lenses
And possibly on some Ukrainian "Arsat" (35mm shift lens)
It means that all these lenses could be set for example on a Nikon body. Obviously without any coupling, but these lenses have no coupling!

Here the "A" ring for Canon Eos provided with the Peleng lens. I added to it an "identification chip" found on the Internet (in fact, I don't use it for the Peleng, I prefer using a M42->Canon adapter ring, which chip is specially programmed for a 8mm lens, it improves the light-metering).