Can anybody tell me anything about this little plate I found?

Interesting idea. Here's an article on flue covers:

https://www.heraldtimesonline.com/s...arden/2019/09/06/intage-flue-covers/47918465/

Debora

 

It would explain why it was in a wall. If the old stove was replaced by natural gas or similar, it wouldn't be needed. When farmers of that era wanted to toss something, it went into a bottle dump or became part of somehing else.

 

I think at 4 3/8 inches, it might be too small for a flue cover, and I don't see any way to attach it.

 

Or was strewn randomly over several acres of woods, as I am finding here on my property.

 

Pretty much. That was their trash dump. There was no collection, so it went into the woods you couldn't/didn't farm.