A Royal Air Force Navigational Computer (Computor) Mk. III H and Manual

WWII Royal Air Force Navigational Computer (Computor) Mk. III H and "Teach Yourself Air Navigation" Book : Navigational Computer with a black metal casing, brass face plates on both sides, obverse with a voided area in the centre with a clear plastic face plate, a white fabric air speed/wind direction scroll containing various charts printed in red ink visible in the body of the computer through the clear face plate, the circular frame brass frame gradated in 360 degrees with eight raised points, right side with a large black plastic knob that enables the scroll to move freely, the brass face plate held in place via eight screws, marked "NAVIGATIONAL COMPUTOR MK. III H", "REF. NO. 68/250", "L.N.P.", "A M" over a large "P" and code stamped "LNP/R/9/50", the left side with a black metal channel affixed to the body that acts as a pencil holder, with a metal L-shaped clip attached to the obverse brass face plate and overlaying the channel to secure the pencil in place, reverse with a central gradated rotating disk held in place via a central pin, the disk with two voided areas exposing a underlying white panel, the disk marked "L.N.P. MFG. CO. LTD. / AIRCRAFT NAVIGATION / COMPUTER", with instructions for "AIR SPEED CORRECTIONS" and "HEIGHT CORRECTIONS", the brass face plate with gradations facing those on the disk, marked "I. C. A. N. CALIBRATION" and held in position via four screws, two of the original four rubber pads in the corners remain intact, 123 mm x 158 mm x 24.5 mm deep, most of the original silvering on the brass plates has worn off, surface rust evident on the metal L-shaped clip, very fine. Accompanied by a book entitled "THE EUP - TEACH YOURSELF AIR NAVIGATION", hardcovered, light blue cloth wrapped, published by The English Universities Press, London, first printing (1942), printed in Great Britain for The English Universities Press, Limited, by the Richard Clay and Company, Limited, Bungay, Suffolk, named in black ink to "R.G. CAMPBELL" on the fly leaf facing the inside front cover, containing eleven chapters (entitled: I - Form of the Earth - Definitions - Direction and Distance on the Earth's Surface; II - Map Projections; III - Elementary Magnetism - The Earth as a Magnet - Variation - Function of the Magnetic Compass - Application of Variation; IV - Deviation of the Compass - Application of Deviation; V - The Effect of Wind on an Aircraft in Flight - Course, Air Speed, Track, Ground Speed, Drift - The Triangle of Velocities; VI - Maps: Scale, Relief, Conventional Signs - Map Reading; VII - Fixing and Reporting Position; VIII - Aircraft Magnetic Compasses; IX - Elementary Meteorology; X - Air-Speed Indicator - Altimeter - Calibration; XI - Ground Flight), with text, line diagrams and charts, perfect bound, containing 184 pages printed in black ink on a thick off-white paper stock, 115 mm x 180 mm x 22 mm, light soiling and wear on the cover, book also very fine. Footnote: This Navigational Computer was specifically designed for aircraft. It computes a myriad of different problems, such as the effect of winds on the aircraft's track and ground speed, as well as fuel consumption/use that is also affected by the winds speed and distance to be travelled/time taken. It can also be used to plot interception problems, in fact almost any mathematical problem that may be encountered in flight. It was used by navigators during the Second World war on aircraft, such as Lancasters and Sunderlands. The maker marks "L.N.P." on the obverse and "L.N.P. MFG. CO. LTD." on the reverse is attributed to the London Name Plate Manufacturing Company Limited of London and Brighton. The mark "I. C. A. N." on the reverse is known to have stood for the International Convention on Aerial Navigation (AKA the International Commission for Air Navigation), the forerunner of the International Civil Aviation Organization (ICAO). Under one name or another, ICAN operated from 1903 to 1945. One of the many things the participants had difficulty agreeing on was what the organization was called. It's various pronouncements are often referred to by the names of the places where the various conventions were held, notable events being in London in 1912 (which allocated the first radio call signs), Paris in 1919 (air sovereignty) and Chicago in 1944 (which established it's successor, the ICAO).