NavList:

Tony Oz you wrote:  I do not have any yet. Mostly I'm interested in the smallest possible instrument. On your picture the one to the right looks smaller of the two, is it the Agfa's?

And in general, would you recommend buying such A-10(A)? I see several on ebay under USD150, are they worth the try?

Tony 

The A10A is simply an A10 with an automatic pecker on it, so it’s slightly bigger.  However, you don’t need an averaging mechanism in a static situation, only in an aeroplane. You I wouldn’t pay $150 for an A10 unless it was guaranteed reconditioned.  I think I paid about $40 each for mine, but that was at least 10 years ago, and they were seized up when they arrived.

The Hughes MkIX BMs were well designed and were in use in the RAF until around 1970, so decent ones come up for sale frequently.  In the early 70s they were being sold off in Flight magazine for £12.50GBP.  I wished I'd bought a few; I might have got back the one I handed in in 1968, but £12.50 seemed a lot in money the 1970s, plus I'd forgotten its number.  Even the original 1940 MkIXs have kept very well although I have to say there’s a lot of rubbish for sale on eBay at the moment at ridiculous prices by the memorabilia merchants.  The main problem with a MkIX is its terrible box, which is completely impractical anywhere other than hanging on the inside of an aircraft fuselage.  If the mounting lugs don't cripple you, they'll scratch any polished surface you put them near.

By far the simplest and most practical WW2 aircraft sextant is in my opinion the Link A12.  It’s light, easy to use, and has by far the most practical carrying case.  It’s just a tiny attaché case.  The Main problems with an A12 are:  You might find WW2 batteries still jammed in the battery container where they might have corroded the aluminium (a question to ask before you buy), although funnily enough, WW2 dry batteries seem to leak much less sal-ammoniac than modern so called ‘leakproof batteries, perhaps they’ve had more time to dry out.  The screw heads are designed to be adjusted with a Bristol key rather than an Allen key, and Bristol keys are much, much more expensive to buy than Allen keys.  Finally, you must be happy reading a Vernier scale, even in poor light. DaveP