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Hmmm ... an adapter to fit the larger American shank into the smaller English receiver would be larger on the inside than on the outside!
There are two possibilities (that I can see):
(1) An American-shank mouthpiece should fit about half-way into the B&H receiver (assuming that the B&H shank is roughly the same dimensions as a bass trombone shank). This can work if you can push the main tuning slide in at least 1/4" (6 mm) further than its "normal" setting (i.e., where you'd set it for the smaller-shank mouthpiece).
(2) Having the receiver replaced with a larger one (or having the existing one reamed to the larger size) is a long-term solution ... but then you'll need an adapter to use any B&H-shank mouthpieces you have.
Hope this helps!
"Don't take life so serious, son. It ain't nohow permanent." -- Pogo (via Walt Kelly)
It's cheaper in the long run to buy either a Wick or a PT mouthpiece in your preferred rim and cup. I have a Wick 1 and a Wick 2 for mine: the 1 is like a Helleberg cup with a Bachish rim, and the 2 is similar to a Bach 18, possibly a bit deeper. The Wick 3 is standard issue with an Eb. With a PT, all you do is add an "S" to the end of the model number.
If it's Boosey & Hawkes, it's not SO old (1934 or newer).
With all the mouthpieces and sizes available, I'm sure that you could get one that fit properly, and not need an adaptor.
Instead of talking to your plants, if you yelled at them would they still grow, but only to be troubled and insecure?
