LaCroix Optical part #16745. Positive Meniscus, 47.975mm (1.889") diameter by 551.49mm focal length. Center thickness is 5mm. Glass is S-LAL12 (high index Lanthanum crown glass). Has special coating providing 99.5% transmission from 1000nm to 1600nm. This is interesting visually because it looks like a see thru aluminized mirror! Very rare. Complete spec sheet will be included with your order. Unused. Only have a few.
