Hi Lou,
Sorry to hear you're having problems with the post office. I still don't understand how they can charge a customer to deliver something, then when it's not delivered they say they aren't responsible for loss or damage if you didn't buy insurance....but that doesn't have anything to do with your dilemma.

Did you take one or more really good pictures or scans of the plate before you shipped it? That could help prove it wasn't damaged before you shipped. Do you have collectibles insurance? That might cover it.

We're doing well, hope you and the family are too!

Pam