u/LibrarianSuperb7702

My house is around 80 years old, and I was replacing some insulation today when I noticed one brick wasn't cemented in like the others. Behind it was a small metal box, maybe the size of a lunchbox. It's pretty rusty but still locked.

I shook it and there's definitely something inside, but it doesn't sound heavy.

I don't really want to force it open if it's something important or collectible. Any ideas on how old something like this might be or the best way to open it without destroying it?

(I accidentally took down the original post. My bad.)