How to distinguish 160 vs 170 mm eypieces?

I have both Orthoplan and Dialux microscopes, and many eyepieces. All second
hand, and ofcourse I don't know what has happened with them over the last
decades, maybe (/probably) eyepieces have been changed.
I've read everything I could find on the web about 160 vs 170 mm, there
seems to be a difference between 160 and 170 mm eyepieces, you should use
the right one on the right microscope (160 on Dialux and 170 on Orthoplan),
but I couldn't find how to find out the difference between the two.

Theo


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