This four-fold boxwood rule has a brass arch joint at the center and two brass hinges. Unfolded, it measures 31.2 cm W x 1.2 cm D x 0.5 cm H. Both sides are marked: No 32. The scales on both sides are numbered by ones from 11 to 1. On one side, the rule is divided to 1/16" along the top edge and to 1/12" along the bottom edge.
The other side is divided to 1/8" along the top edge and to 1/10" along the bottom edge. A brass caliper slides out from the right end of the rule. Both sides are divided to 1/16" and marked: 1, 3/4, 1/2, 1/4. The underside and the slot in the rule are also marked: 58. The divisions are all roughly made; the instrument does not appear to be machine-divided.
The Stanley Rule & Level Company of New Britain, Conn., offered model number 32 from 1859 to 1941. The shape of caliper jaw found on this instrument was introduced between 1888 and 1892. An illustration from a 1919 Stanley catalog indicates that the company name was stamped on the ruler by that time. A similar folding pocket rule with caliper is advertised as model number 1752 in Catalog of Eugene Dietzgen Co., 7th ed. (Chicago, 1904), 167. Its price was 60¢. The Department of Entomology at the National Museum of Natural History used this rule to study its collections.
Reference: Philip E. Stanley, Boxwood & Ivory: Stanley Traditional Rules, 1855–1975 (Westborough, Mass.: Stanley Publishing Company, 1984), 95–96.