This pocket tool was invented to make calculation easy. It features only subtraction and addition but was way cheaper then an electronic calculator at this point in time. It comes in the original leather case and with the original aluminum pen. On the top is a little pull out handle to put the numbers back on zero. It shows that the original owner used this handy tool! Real nice piece, measuring 15,5 cm / 6 inches. Here you find the original 1972 advertisement for the US.