G-S Flexo Watch Crystal Y613 for Longines Fulton

This is a vintage G-S Flexo watch crystal, specifically the Y613 model designed for a Longines 'Fulton' watch. It's still in its original paper envelope, which lists the dimensions as 20.9 by 19.1 mm. These are great for restoring older timepieces to their original look. New old stock condition.