Another one in the list of Tomioka fifties:
Auto Yashinon DS-M 1:1.7 50mm.
I have a love affair wih Yashinon-DX lenses because they are usually quite good, and also very well built.
I find them very practical too, cause they have the A/M switch, which allows to quickly shift between wide open and the chosen working aperture.
The DS line has no switch, so you either need to modify the lens, sticking the pin in depressed position, or use one of those black adapters that have a little internal flange that keeps the pin down.
The DS-M family has no A/M switch too, but has an important improvement over the previous series: multicoating.
No other Yashinon lenses in M42 mount are MC.
Successive DSB and ML lenses were multicoated, but had a C/Y bayonet.
This is the reason behind my purchase. I am curious to see how a modern anti-reflection treatment improves the performance of a good design.
I can't wait to test this new (to me) lens, and see how it compares to similar designs, for example Pentax f/1.7 MC objectives.
I tried a couple of Tomioka single-coated low-cost fifties (f/2 50mm) with impressive results. Faster Tomioka's, like the Revuenon 1.2/55mm and Chinon 1.4/55mm, are among my best lenses.