Manufacturer's part #02 MFG 018 (doing a simple "Google" search of this number will show you who the manufacturer is). Their price: $98. Made of LEBG (low expansion borosilicate glass similar to Pyrex), flatness is 1/4 wave (top is polished, bottom is fine ground), thickness is 10mm, parallelism is 3 arc minutes. Unused! Not Aluminized. Could be aluminized to make a high reflection mirror or used as a mirror in applications where only a small amount of reflection is wanted such as sun reflection or certain laser applications
