Gary
Not to quibble or anything, but the guy on your link who you claim DOES KNOW something about Brandis Sextants, Mr. Morris, describes the instrument held by Admiral Byrd as being a sextant:
"I recently acquired a Brandis nautical vernier sextant without case, telescope, or any shades. It appeared to have an extra mirror in front of the horizon mirror and I recognised it as an early bubble sextant of the type used by the then Commander Richard Byrd on his claimed flight to the North Pole in 1926. There are several magazine photographs extant that show Byrd in posed pictures, using a similar sextant, this one, for example:"
Then he goes on to describe it as a quintant:
"The one Byrd is using is a full-size Brandis vernier quintant with an arc of 180 mm radius reading to 30 seconds, whereas my example is unusually small for a vernier quintant, having an arc radius of only 140 mm, also reading to 30 seconds,...."
So, what is it, a sextant or a quintant?
Seems your expert can't get it right either, and is prone to the same problem as Mr. Jacobs, calling all of these instruments generally "sextants" and then further refining that depending upon the actual arc covered by the instrument.
I think you might cut a little bit of slack to Mr. Jacobs if you are going to tout Mr. Morris as being an expert. You can't have it both ways.
Andrew