This is a very nice slide rule type calculator, with previsions for calculations on both sides. This calculator is designed to reccomend various FUSETRON or LOW-PEAK fuses for various Horsepower motors with various Phase options. We have supplied some close up pictures for more details. It is marked "BUSSMAN MANUFACTURING DIVISION MCGRAW-EDISON COMPANY ST. LOUIS, MO 83178 MOTOR-RUNNING OVERLOAD & BRANCH CURCUIT PROTECTION GUIDE". The calculator is in good+ condition with a few minor scrapes and smudges, the slide moves smoothly and all is clean and readable. This one is made of plastic covered heavy paper, with metal rivots. It measures 6.45" long overall. A nice clean collectible slide calculator!