I need to swap crystal on circa 1970 SSW. Can anyone let me know the correct wrench reference please.

I am sure there was an official tool at some point, but I have never seen one.  The SSW crystals are not easy to replace, and there are so many different variations in crystal size over the years of production that it is hard to ensure you are buying one that will fit correctly.

There was an official one long ago but they are all gone now. I have used many types of wrenches over the years. No guarantee your crystal will just drop in though, but hope so!