These little SHG units are from JDSU and LWE (light wave electronics).

They are used and all have varying amounts of degradation around the perimeter of the crystal. All have use left as long as you keep the beam in the center 50% of the crystal.

First sold will be the best condition and last will be the worst (shown in last photo).

Crystals are 3x3x5mm AR coated both sides and are in gold plated copper mounts. The little tecs are 1/2"x1/2". I believe the thermistors are 10K