One of two 60 degree glass prisms with beveled edges and 3 frosted faces including the base. A small capital B has been written on one frosted side in pencil near the base; labelled as small with reference to the counterpart larger prism b
Plastic covered slide rule with a ruler on one edge and sine function on the other. On the back there are some instructions and tables. Comes in cardboard box. Made by CASTELL, on box in gold lettering.