Help with Nazi Blue lens

[coyotecolo]

I'm not sure where else to post this, so I'll give this a try.
I would love to find out what this was, it clearly is a blue glass lens that was mounted to something. It measures 2 3/8" across.
It has the swas inside the iron cross, and writing around the edge.
Does anybody know what I have?
Thanks in advance.

[coyotecolo]

more pics

another look

[nickn]

Veterans association badge

[coyotecolo]

more?

But what would a curved blue glass lens be used for? I'm curious about how it was used, maybe over a light source?? maybe will never know, but if anybody knows, it will be on this forum I'm sure.
Thanks

[Mikedenmark]

Possibly for some kind of lamp?
Blue light hints at blacked out cities.

But, that only really happened when the war started. And by then, to make fanzy glass ware like this seems less probable.
The text says member of the National Socialistic warrior(veteran) association, so it is for personal use, not a lamp outside an association office.

[nickn]

It's not a lens it's for fixing on to a car or door I believe
One in my collection has black over paint around the edges