Water resistant Pocket Watch, Model 10109, 'Les Traditionelles', Cal. Unitas 6498

Opening the watch was actually quite easy using a
Cricket practice ball made from rubber. I saw an employee at my watch parts shop using such a Cricket practice ball and at home, I had to give it a try. And indeed, the relatively sticky surface of the Cricket practice ball worked magic on this case back. The crystal can be removed the same way.