Barrel slide rule with two varnished cardboard scales within a metal casing. The lower scale is a single cycle logarithmic helical scale fixed to the bottom of the instrument and is called the holder. It is the equivalent of a sixty-six inch slide rule. It is marked Scale No 414. The holder and the bottom scale form a tube which houses the cylinder with the upper scale , a two cycle logarithmic scale which is effectively 132 inches long. The upper scale is numbered Scale No 423. The top metal tube has two arrows opposite each other, one on the bottom of the tube and one on the top. These are used to read the scales. The scales are for multiplication and division purposes.