NavList:

Brian Villmoare you wrote:  I just inherited a Mark 5 bubble sextant. Compared to my A-12 it has a lot of levers and buttons that seve mysterious purposes. Is there a manual anywhere out there that explains all this?

Brian
Before we go any further, are you talking about an RAF MkV sextant, or a USN MkV sextant.  The RAF MkV looks like this https://hydrography.pro/presta17/octant/619-er-watts-rae-sextant-mk-v.html .  If it is an RAF MkV, you’ve got a rare relict.  With no instructions, you’ll probably have to try each function in turn and see what happens. By the way, rae is not a typo for 'rare'.  It stands for Royal Aircraft Establishment.  You might also find the following useful https://www.gracesguide.co.uk/E._R._Watts_and_Son .  On the other hand, a USN MkV looks like this.  https://timeandnavigation.si.edu/multimedia-asset/mark-v-sextant .  There's a description and photograph of the USN MkV on page 185 of 'Taking the Stars' by Peter Ifland, but I've mislaid my smartphone at the moment, so perhaps someone else might oblige.  DaveP