Need help identifying a shotgun

[Freebird01]

Weird question… does your father in law have any ties to Europe?
I went down the rabbit hole on this one.
When I say converted, it may have been by the factory. The Marlin 54 never had a floor plate as far as I have found. However, an older than dirt gunsmith (retired) said he vaguely recalls the 55 Goose gun coming in a rare single shot that he thought was marketed for over seas due to some restriction. He said you would know if the plate was removed and there was a hole and a plug were the magazine would have been. I’m still digging. If you took pictures from the top with the bolt back or removed he might be able to tell. However, I’d have to print them and take them to his house lol.

Nope...Philly boy his whole life