Mount Vernon C question

[dukesboneman]

I was gifted a H.N White late 50`s 3B and it cam with a Mount Vernon 7C
But it plays different than my usual Mount Vernon 7C
It has ,right below the cup before the rings start, it`s stamped "G"
and below the rings it`s stamped "420"
Plus the inner rim is really sharp. Articulations are so easy and clear.
What can you tell me about this mouthpiece?

[Posaunus]

My guess:

• The "G" represents the throat diameter [G drill = 6.63mm (0.261")]

• The 420 represents Bach's #420 Backbore

This would be the same Throat and Backbore as on the larger/deeper-Cup Bach 6½AL and 5GS mouthpieces.

Apparently the owner of this 3B wanted a larger Bach mouthpiece with a sharper Rim, which in those days Bach was quite willing to supply.

How do you like the way it plays? I would guess much bigger than a "standard" Mt Vernon 7C!
I think I might enjoy playing it.

[TromboneMonkey]

I have a very nice Bach MV 7c which also has a much more pronounced inner bite than other 7cs I've tried. The rim is also a bit narrow compared to my other 7c rims. It locks in really well.