Makoohr, thanks for the pictures. As I thought, they're standard A-profile ANSI dyesubs.
As I explained to you in PM : Yes, the G81-3100S
BU has never been seen before, but there is no difference between a G81-3100S
BU and a G81-3100SDU or G81-3100SAU that would be of interest to any collector. The difference in the middle letter on 3100 boards signifies differences in the card reader or additions like a heavy duty cable. See below :
No collector today cares about differences like these. Realistically, most collectors only care about the keyset and some collectors (like myself) would value the whole NIB keyboard as a piece of history. However, nobody would pick and choose between a G81-3100SBU and a G81-3100SDU. They're the same visually, which is all that matters when it comes to G81s since the switches are so bad.
To illustrate what I mean further.. Do either of these look any different to yours? Because they have different middle letters. Actually, one of them isn't even a 3100; it's a 3116. But not even I would be able to tell you that from looking at it.
I hope this explains things fully. Great job finding them too.