Very rare unit Marine Flak 214 which was stationed in Cuxhafen Germany. The construction is completely something I had never seen before as a long time militaria dealer.
I finally found a small online group after 10 years of searching dedicated to the unit and whose members had one or two other. When I asked If the construction on these the admin gave me this info This plastic layer above the coat of arms is most likely transparent Bakelite. This synthetic resin-based plastic is considered one of the first of its kind. However, it contains approximately 5% asbestos. As you can see in the photos somehow it is backed into the pebbled glass.
If you google marine abteilung 214 Cuxhafen you will also find more info. The Christmas gift decal on the reverse is signed by the Commander at that time LT. Bley A very rare original German Flak item.