This is a 12.5" full thickness pyrex F2.7 polished out RC primary mirror. This was owned by a retired optician at Tinsley Labs but I have never done anything with it. The owner was a professional optician but I do not know what state of completion the glass is in although it is polished out. I don't have the time or the funds to complete this into a complete RC optical system. I am pricing this as a blank. Condition is nice used with a small chip on one edge of the center hole. The secondary for this mirror will be quite large so this small chip will not be seen at all.