M42 Ext tubes anyone?

Bought these a few years back and the description just said pentax extension tubes. They are M42 and of no use to me. There in, I would say, unused condition, the mark on the bottom thread is from me testing the fit in a batterd M42 mount today, the thread works perfect. The box has seen better days though! There very well made. Automatic.

I dont need 'em, I'm open to offers or swaps.