Putting this back up for sale. This is an AUTO-M42 lens, so the aperture is stuck wide open @ 2.8 UNLESS you have a tech modify the lens to keep the aperture pin stuck, or buy an adapter that will depress the pin and allow manual aperture. I wouldn't imagine it would be terribly expensive to get that repair done.
It's a filtermatic lens so it has three filter inside the lens (a blue filter, yellow filter, and UV).