Faber Castell 1/61/361 electro slide rule in case 1938 Germany

Unusual slide rules by Faber Castell in the original box from 1938. It has the number 1/61/361 or just 1/61 as shown on the box. It is a Mannheim type. The rule and cursor are all complete and all in good condition with signs of use (2 small dents on the right hand side). There is some yellowing to the (original) white layer over the wood.The original cardboard box is complete but has clear wear to the top ends. The rules measure ca. 30 cm or 12 inches long. Check the attached video on how to work your vintage man tool: slide rule operation instructions!