I am not sure if this lens is complete. It seems to me, from the picture, the camera mount is missing. It's true that these lenses came with Pentacon six mount, but they have also been made in much bigger amounts for Exakta mount and M42 P-mount. As far as I recall the Pentacon 6 mount was a mount bayonet like mount with three evenly divided metal parts over the ring that I don't see here. It seems to me this is a screw mount type of fitting that is similar to a T-mount adapter. Anyway for all of these fittings relatively cheap adapters can be bought for EOS, Nikon and NEX mount. Though this lens is an impressive piece of metal and glass with typical mechanics from the VEB/Pentacon machinery of the 60 and 70ies, this is not the most impressive piece of optics. It's a so called long focal lens design instead of a more compact designed telelens. This as far as I recall a achromatic 5 elements lens design and it definetily has all the glass in front elements far from the shutter. CA is noticeable just like some distortion because of the asymetric position of the aperture mechanism.
Asking prices for this glass are typically between 160$ and 250$, but I doubt they are sold for that amount, unless it's a mint copy attractive for the collector. As a telelens for modern cameras they are less useful and behind even most modern zoomlenses.
Anyway good luck with sales. I am sure you'll find someone who loves this big pipe for it's focal length fitting on a modern Nikon, Canon of NEX body if you ask a reasonable price.
Thanks so much for this information! It looks like the mount may be some kind of hoya adapter. I wonder if there is an m42 screw mount under this. It didn't seem like it unscrews.
I had the lens in a M42 screw thread . Mine was chrome or bright metal finish. Would say it was only a fair lens, heavy metal for sure. I also had the black one like shown. I had Tempe camera repair remove the Pentagon mount and mount a Pentax 6 X 7 lens mount that i purchased from Pentax parts dept. Again it was only fair on my Pentax 6 X 7. I agree something appears covered up or possibly missing.
Harry Palmer