Surprise keeps coming: lens mount help

[vivaldibow]

With more than 10 different lens adapters on my desk, I thought I know many lens mount types already. However, surprise keeps coming.

Got this Vivitar 100mm f/2.8 SN 408xxxx, the last one in my wish-list for non macro Vivitar 100/105mm's. It is a 3-lug bayonet mount with a notch in one of the lugs. I tried it using a Pentax PK adapter, it fits, but doesn't lock. Here are two photos showing the mount. As I am posting, I found the mount can be screwed off, the lens seems to be a T mount lens.


#1


#2


Thanks!

[Oldhand]

Resembles Contax Yashica mount to my eyes.
Can't be sure though
Tom

[Lightshow]

Looks like C/Y with some other adapter attached to that, So if it is T mount, you have 2 stacked adapters.
The notch in the tab rules out a bunch of possibilities, of those, it's not Konica AR, Minolta SR or QMB.
look on page/Part 2
https://www.keh.com/blog/the-lens-mount-guide-part-1/
https://www.keh.com/blog/the-lens-mount-guide-part-2/
https://www.keh.com/blog/the-lens-mount-guide-part-3/

[vivaldibow]

Thank you guys for your answers. I don't have the lens with me, but I guess it could be just plain M42 (not T)
with an M42 to *** adapter.

I searched the M42 to C/Y adapter and found it is very similar to the one on the lens. I guess it should be it.
The M42 C/Y adapter doesn't seem to have the tabs on a native C/Y mount.

[monopix]

Yes, definitely matches a C/Y mount. I would remove it and get a proper M42 adaptor for whatever camera you have. The M42 flange distance is shorter than the C/Y so the M42 lenses on a C/Y camera don't focus on infinity.

[vivaldibow]