dsio
··Ash @ ΩFDoes plexiglass/etc have more a tendency to change shape over time?
Honestly I'm not sure. What I do know is that the Rolex Submariners (1680 and 5512/5513) and the Omega Seamaster 300 diver, which were rated to 200M / 660Ft were at the upper limits of what was possible with plexiglass, IIRC the deeper diving watches of that era either had extremely thick crystals like the superdome on the 1665 Sea-Dweller or mineral crystal as I believe the PloProf 600 had.
The Sea-Dweller 1665 Tropic 39 is just stupidly thick, as you can see below compared to a 5513 Submariner's 5513:
Of the two the Seamaster 300 is closer to the T19 of the 5513, and the dome probably does give it some added strength, but still plastic is plastic.