Original Air Ministry Bubble Sextant Mark IX BM. In excellent condition. Made by Kelvin & Hughes. Unlike sextants that rely on the horizon as a reference, the Bubble Sextant utilized an internal bubble for alignment. This innovation made it suitable for airborne use, where the horizon might not be visible. This (very rare) BM is the most elaborate of the Mk IX bubble sextants produced by Hughes. It has both the telescope as well as the integrator with a choice of either a one or a two minute integration interval. Because the timer is slightly larger the case had to be extended with a circular extra lid. The intrument is complete with all the original accesoires and maintenance booklet. Even the batteries are original. The case is made of beautiful shiny dark brown bakelite. Weight: 5,5 kg.