These are Fused Silica substrate Mirrors from the upper bread board on a Coherent Avia laser. "number 4" in the laser photo.

I have 2 available with the complete gold plated mount consisting of 2 halves with solder in between.(see photo) 

I have several with only half of the gold mount. These were removed from decommissioned lasers for one reason or another. 

I also have some that I removed the gold mount part so you can install it in a standard 1" mount.

There are a few with damage to the back of the mirror which does not affect the working side. 

Tell me which type you want. Full mount, half mount or no mount. All are the same price.

I combine ship as well.