Graphoplex BP combustion efficiency pocket slide rule 1960 France UK

This slide rule has been specially constructed for British Petroleum by Graphoplex as shown on the back. The front has scales for calculating combustion efficiency and losses in percentages for gross and netto loss at set CO2-levels, at set temperatures (Fahrenheit and Celsius) for oil. On the back of slider are more scales for additional calculations concerning air and oxygen as well. Making this a very dedicated pocket slide rule. It also comes in the original BP signed leather sleeve. The curser, rule and sleeve are complete and in very good condition. with minimal signs of use and age. It measures 15 cm or 6 inches. Do check the attached video on how to work your vintage man tool : slide rule operation instructions!