I would be questioning the authenticity of that plaque. The engraving looks as fresh as if it were done today and is badly executed. Some of the others I saw were more convincing, but, as you said, where would they get them from? If something smells fishy............

I can't imagine why anyone would buy something that memorializes such a horribly sad event, unless it was to get it back in the family. I found this via a google search:

The history of Coffin Plates or casket plates is a long but not very
well documented one. Coffin plates are decorative adornments attached to
a coffin that contain genealogical information like the name and death
date of the deceased. In Victorian Times (and earlier) the coffin plate
was removed and presented to the family as a memento of the dearly
departed.

With almost 500 coffin plates now online,
AncestorsAtRest.com is the largest repository of these wonderful
genealogical treasures. Each coffin plate has the name of the deceased
plus date of death, and usually date of birth. Images of the plates are
provided. You can search these coffin plates for free - who knows, you might find an ancestor or two!

I have one that says "At Rest". I bought it about 55 years ago. As I recall, there were tons of different ones. I don't know why I chose that one.