Towards a Polarouter/Polerouter case typology

I've noticed variation among the Polerouter cases in my own small collection, even within a movement family. I've started some research to describe the various Polarouter/Polerouter case types and to figure out how they correlate to Polerouter/Polarouter case reference numbers. While the case reference code has apparently been cracked for the chronographs (for example, see the table on Sala page 88), I have not seen an analogous taxonomy for Polerouters/Polarouter cases. Once I have a little more time, I'd like to get this sort of thing rolling, with help from all of you.

In the meantime, I'd like to share with you a nifty and recent article I found in my web searching, one which even references some of the ideas and pictures we've discussed together on this Forum. It is a very handy piece of work, albeit preliminary and partial in scope. It attempts to make sense of some Polerouter reference numbers: a job I think we can elaborate on and complete together in time. I'll leave it at this for now; more another time.

https://thespringbar.com/blogs/guides/universal-geneve-polarouter#heading125

Yes I agree, I had some Polerouter with HF cases and for almost of them the case was slightly different from a watch to another.

I had a 215 from 1955-57 and in comparison of my actual 215 (gold caped) from 58 the case was larger with bigger lugs (36 vs 34,5mm)

And in comparison with a 218-2 from the last 50's the case has the same width but different shape of the lugs!

I can't wait your analysis A.