Stephen.., Don't fret.. These are usually glass and have been made for many years. Problem is,,they still make them the same..
Those that want to collect one for their 3rd reich era collection there are a couple things you can do:
First,,if it looks brand new it usually is!
2, Look for the European content marks,,,830,835,900. 925 is a non starter for me even though early on some were seen. On a iffy ring to start with you don't want 925.
3rd,band style! You really go to look / study the styles. Wether from old catalogs or from the internet.. Once you start actually looking/studying you start to see what is 20s-40s as to latter more current..
Yours is a possibility,,,don't ditch it. Hold on to it until another more convincing to you comes along!