SME Baseplate Question

First of all - apologies if you have seen this posted elsewhere.

Can anybody tell me what the interior dimension of an SME baseplate is. Specifically the portion that accepts the tonearm's vertical post.

A different way to ask: can anybody tell me the diameter of an SME mounting post?

I have an infinity black widow tonearm and I am missing the mounting baseplate. my turntable is cut for an SME type/sized baseplate mount which is actually what the IBW comes with as stock.

Given that an IBW mounting plate on it's own will be unobtanium i am trying to figure out if purchasing an SME baseplate off of some auction site will solve my problem.

the IBW's post is 15.45mm in diameter.

Any help here would be appreciated.
According to my digital caliper, my SME V-12 mounting post or vertical arm column/bearing housing is 23.10 mm or 0.910 inches in diameter. You could also try emailing SME directly for this dimension or looking on the spec sheet on their website.
I have a possible solution. Back when I was messing with
building arms, turntables and other phono stuff, I built a
pseudo-SME bases and I have 1-2 around.

I have a nickel-finish one with the SME hole (too big for
and I have a black one with an approximately 15mm diameter
out. Of course, it could be drilled out a bit if necessary.
Fits a standard SME cutout and mounting holes. It is 1/2"
thick, so it requires a relatively thick platter above the
arm board.

Let me know if you are interested.