i think the guys that did the measuring might have made a misreading. i think this one is a .450 proberly a 3 1/4" as Mr. henry liked to push the envelope a bit. this is a best gun as that action were only used on his best guns.
i love the case but am a bit sad that all the goodies are gone. the caliber is easy to get as all it takes is a phone call to the book holders. other than that it looks like a good gun.

best

peter