NavList:

Geoffrey Kolbe you wrote: I see from the manual that it was issued to the RAF. I wonder if David Pike has memories of it?

Were you talking about the A8 or the A12 sextant, and which manual did you read the reference to the RAF in?  Notwithstanding the fact that, according to the vendors, almost every piece of aircraft junk more than 40 years old advertised on eBay, came out of a Spitfire or a Lancaster, and every piece younger than that came out of a Lightning or a Vulcan, I know of no large-scale use of an American bubble sextant by the RAF until the limited use of periscopic Kollsmans post 1950.  They had arguably better Hughes sextants of their own.  I can think of one or two occasions when a ‘stray’ might have been encountered.  To pin this down to an A8, or A12 we would need to know when each was first introduced.  Rather than stab in the dark, we can talk about this more when you tell us which sextant and which manual.  DaveP
P.S. If you don't want your second A12 bubble, there's an empty space in my A12 box looking for a lodger.