Fowler was best known for making pocket watch style calculators.

One face has a long-scale and short-scale logarithmic scale. The short scale could be used for rapid calculations or as a check that the correct sector of the long scale had been used. The other face has a short-scale and reciprocals, logs, square roots, sin, tan and sin-tan scales.

The rule is in perfect working order with both the dial and the cursor moving smoothly. The glass on one face has two small hairline fractures. The "loop" from the larger of the knobs is missing.

The rule is provided in its original leather wallet lined internally with red velvet. The wallet is embossed "With the compliments of HOMATRA LIMITED, British Oil Burning Systems."

The rule will be provided with a photocopy of the original instructions (from another rule). These are slightly difficult to read as some words were barely legible at the folds lines so a photocopy of printed instructions I prepared from them will also be provided. These instructions can be seen here.