OK...I've got the REPLACEMENT production prototypes...
They're both "on the money" (inside dimensions) and I'm giggling, as they match my crappy-lathe bloke-shop prototypes.
The SMALL shank (which not-so-many of you will be ordering, but still...) EXTERIOR looks to be a few thousandths larger than my prototype, so I'm ONLY going to have them send a 2-inch-long solid (not bored) tapered CHUNK to verify the need-to-be-slightly-corrected small shank dimensions.
I REALLY WOULD recommend - to those of you who own F cimbassos (and most of you likely own the large-bore Jinbao ones, which doesn't make any difference) - considering ordering this shallow-cup mouthpiece (but in STANDARD shank - as that's the Jinbao receiver size). I believe you might (??) enjoy playing those instruments more - with one of these mouthpieces.
At the same time (since - so far - they've not sent me any prototypes with the large "euro" shank) I'm going to ask them to send a similar solid test tapered large/euro shank "chunk".
As of today, their shop is closed for a couple of weeks (annual scheduled vacation), so (once again) a bit of a delay/detour, but WE'RE GETTING THERE !!!
I would post pictures, but the exteriors look the same as the others (other than a bit of i.d. stamping, rather than felt-tip markings).