Anybody know about this mouthpiece?

[KDT]

Hey! So this is one of my first actual postings so pardon the formatting and me being extremely uninformed about trombones.
Alright so I recently bought a horn from a house sale, it’s a super roughed up horn. No idea the exact model, but it has the engraving Elkhorn Pan American (pretty sure it was an old company, right?) and it came with this mouthpiece. It’s super roughed up, like I mean it’s got dings and scratches and it looks like somebody stuck their nails in butter. The only marking on it is “Imperial” along the top. It’s kinda stuck in the trombone, planning on washing the horn and hoping whatever the cause for stuck-ness is removed. Thanks and once again forgive my poorly informed and poorly written post!

[balkansobranie]

Boosey and Hawkes produced trombone mouthpieces (and trombones) in the UK under the "Imperial" brand in the middle of last century. Normally they would say "B&H Imperial" along the top. If you google it you will find images. Not sure when they stopped making them, but they fell out of favour in the UK in the late 1950's when the embargo on imported instruments was lifted and professional players switched over to American instruments, mainly Conn in the case of orchestral players. Interestingly, Denis Wick played a B&H Imperial Trombone while he was a music student.

Your trombone is a typical American band instrument, but as a British trombonist, I am wondering how common it was for players in the USA to be using British mouthpieces? I am guessing that wasn't very common.