Slide Rules from TOS Computation Units

TOS home

[Click on the photos for (much) larger views.]

Basswood 205 mm slide rule from unit 209. (This rule can be seen with its cursor in place here.)

Basswood 152 mm slide rule from unit 273.

Both of the slide rules shown above were manufactured by Engineering Instruments, Inc., Peru, IN (originally known as Lawrence Engineering Service, from Wabash, IN). The company moved to Peru in 1938 or 1939, and changed its name in 1947. The larger rule (from unit 209) appears to be an unbranded version of Lawrence Engineering Instruments model 8-B, without the usual conversion chart on the back. The smaller rule (also with a blank back) appears identical to the Lawrence Pocket rule.

TOS home