so, thanks to @Noir I now know what the metal "ring" over the dial is...
lo and behold
The armoured acrylic crystal
lo and behold
The armoured acrylic crystal
Removing and Inserting Armored, Tension Ring Watch Crystals • Adjusting Vintage Watches
This post describes how to remove and insert armored, tension ring crystals into wristwatch cases.
adjustingvintagewatches.com