Manufacturer's part #02 MFG 001. Original price: $46. 6mm thick, wavelength range is Visible, Near IR 400-800nm. Clear aperture is 22.5mm, surface quality is 60-40 scratch and dig. Polished to 1/4 wave on the top and ground on the bottom. 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. Unused.