This is a sapphire replacement crystal for the Omega 600m "PloProf", custom made to be an exact replacement for the mineral glass crystal supplied with the watch. It uses AR coating on the inside.
Crystal replacement should be done by a professional watchmaker. Each crystal is carefully inspected for scratches and defects. Exchanges are not available and returns are not accepted regardless of claim.
OCEAN7 Watch Company is not associated in any way with Omega S.A. This crystal does not fit the LM-7.