The back is stamped: "Johnston Brothers, Inc.;lPackaged Boiler Manufacturers; Ferrysburg, Michigan; Pioneers of Submerged Rear Combustion Chamber Boilers." Also has the Johnston Brothers Logo in green. The object consists of the slide rule and case.
Johnston Brothers, Inc.
Donor's ID number for rule
overall: 1/4 in x 6 1/4 in x 2 in; overall: 1/4 in x 6 in x 1 1/4 in