G-S Flexo CO306 Watch Crystal for Gruen

This is a vintage G-S Flexo cylinder watch crystal, specifically made for Gruen watches. It's the CO306 model, measuring 13.5 by 11.1 mm. It's still in its original paper envelope, which has that great old-school watchmaker look. Perfect if you're restoring a classic Gruen and need an authentic replacement part. New old stock.