Blundell Torpedo spread Slide rule navy 1960 England

This is an interesting and large dedicated slide rule made for the UK Navy. It was for the use on submarines to determine the spread of multiple torpedos in 1 salvo (up to 6 torpedo’s). The correct spread would lead to the highest succes rate. It was  produced by Blundell from England with patent numbers on box and rule. There are no instructions but it comes in the original wooden box in very good condition and fully functioning as does the rule of course. It is an unusual heavy all plastic construction, no cursor was used on this model. There are 2 sliders (the back is all blank), so I assume the instructions were in the general instructions for the submarine firing crew.  Everything is in great shape with hardly any signs of age and use. The slide rule measures ca 33 cm or 13 inches wide. Check the attached video on how to work your vintage man tool : slide rule operation instructions!