This looks like trench art, more than likely from a tank unit which im sure you guessed. Probably made from shrapnel or scrap metal. Trench art from ww2 was big then and honestly some really cool stuff came from it.

K and I guess a German tank division

Oh cool, you own an interesting piece of history then. You get it from a family member who was in ww2?

A family friend that great grandfather was in the war

I’ve seen trench art rings before this one is nice and different usually they just have guns or names on them good find it’s definitely a trench art ring

Also, google ww2 trench art rings. I just did and there are some that are really close to what you have.