Martin PBM-3 Flying boat load adjuster circular slide rule full set 1943 USA

This round slide rule is a balance computer (BALCOMP) aka load adjuster, marked to be used specifically for the Martin PBM-3 and PBM-3C Flying boats. Between 1940 and 1949 only 1366 were build (see also wikipedia) of which at least 800 were other models like the PBM-1 and PBM-5. These Flyboats were used around the world, both in war as in the US Coast Gaurds. Only 1 serviced and is in the Coast Guard Museum. The slide rule was made by the same company that build the PBM Mariner, The Glenn L. Martin Company from Baltimore, Maryland, USA. It is marked 1942 in the middle, the original crisp manual is marked 1943. I also comes in the original leather case with company and model name imprinted. The slide ruls is made of metal with 2 plastic cursors. It is in good working condition with some signs of age mostly. Some darkening to the 2 cursors and some sun staining on front and back. Hardy signs of use. It measures ca 15 cm or 6 inches in diameter. Check the attached video on how to work your vintage man tool : slide rule operation instructions!