Vintage Comptometer Adding Machine


This is a 1950′s Monroe “Executive” comptometer adding machine, a precursor to the modern calculator/computer.  It is a portable hand-cranked calculator that was first introduced in 1929 by Frank Baldwin and businessman Jay R. Monroe.

Monroe saw a need for a simple and portable calculator for business applications, which could be used with minimal training, and which would perform all four arithmetic functions with equal ease. He recognised that Baldwin’s latest design had the potential to combine the rapid setting of the key-driven machines with the full arithmetic capabilities of the rotary calculators, and a partnership was formed to develop the machine for production.

Monroe “Executive”, Model L-160X
Technology: Stepped drum, portable
Weight: 8 pounds (3.6kg)
Manufactured: Monroe, New Jersey, 1929

It has a sloping keyplate with a uniform key height. The carriage is a one-piece aluminium casting which contains the accumulator and counter registers. There is only a single clearing handle, which is rotated clockwise to clear the counter and anti-clockwise for the accumulator. The carriage can be moved one step at a time by half a turn of the T-handle (missing) at the front left of the machine, or continuously by lifting the knob at the right-hand end. The front of the carriage rises a little during shift or clearing operations.

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