Hello!
My grandpa always wanted to know what this (http://imgur.com/a/z2JY2) heraldic plate could be. He asked two experts on the subject, but none of them could answer precisely about its meaning or history. We only know that its shape was common between 1375 and 1475 after J.C, and that's why I came to this subreddit!
I hope the historians of reddit will be able to help me and my grandpa to discover what that plate really is!
Thanks for your attention!
This looks very much like a decorative tin plate of the kind that was very common in Central and Northern Europe in the 19th and 20th centuries. I'm afraid it isn't older than that. Unfortunately I wasn't able to find out what exactly the heraldry refers to. Honestly I think you'll probably have more luck in /r/whatisthisthing.