How can I look up a crystal for my 1964 Tissot seastar?

I have a 1964 Tissot Seastar (Not a Seastar 7) manual wind with a nasty cracked plexi-glass and want to order a new one. I am guessing it changed out like a traditional crystal since the case back comes off and I can see how the movement removes. I have a press for changing it if it is a traditional type of install.

The movement is a 781 caliber
The number on the movement is 6810562
The case back is 41500 42500-9