Thornton 3470/52 boat propeller British oil slide rule case 1950 England

English made beautifully made slide rule with dedicated cursor, made by PIC/A.G. Thornton from the 1950’s. It is the type 3470/52 (patent applied for, probably in 1952) and was specially produced for / with Associated British Oil Engines (Marine) Ltd. and also signed National / McLaren and Mirrlees on the lower side. It is used for calculations regarding boat engines, like propellor speed, shaft horse power and Knots vs diameter ( on the back on of the slide also slip and pitch. The cursor has numbered hairlines.  It comes in the unsigned but I think original green cardboard box. It measures is 30 cm or 12 inches long. The slide rule is made of mahogany with metal peg fixed lamination. Ink in red and black with logos in blue (everything engraved). This piece is in great overall condition with minimal signs of use and age. Do check the video below from youtube on slide rule operation.