There are many online archives of newspapers and magazines, such as archive.org. On this page I will show various advertisements by Monroe that I have found in such online archives. If you find any others in the archives of your own country, then please let me know at mechcalc a t jaapsch d o t net.
These advertisements are shown here for educational and research purposes only, and no copyright infringement is intended. If you are the copyright owner of any image, and object to its presence here, let me know.
The oldest advertisement I found is from October 1914 for the model D. These ads depict a machine with pins on the front of its carriage along its whole length. This was changed in 1915 in the last models D and the model E, but the ads showing this continued for some time after that.
Model E and F (and the last model D machines) have a wavy comb-shaped piece between the keyboard and the carriage which is used to align the carriage exactly, and a row of holes on the left end of the carriage and a hook which uses them to lock the carriage down. The first appearance I found of this in an ad is in March 1916, even though the model E came out the year before.
From February 1919 onwards the ads show the model G calculator. Instead of a row of holes it has a rail on the front-left of the carriage onto which a hook grabs to keep the carriage in place during a calculation. The model G was likely introduced in 1918, and the ads were not either updated or the earliest model G calculators did not yet have that rail.
The model K is easily recognised by the rounded case. I have mostly found ads from 1923; very few early ones from 1921 or 1922, and also few later ones. Given the popularity of this model I expected to find more.
The model L is much smaller than the model K and has cylindrical buttons instead of flat button tops on metal stems. From 1934 onwards the Monroe-Gardner adding-listing machine was also advertised, as well as bookkeeping machine versions of it.
From this point on Monroe made the Monro-Matic, and other similar automatic and electric machines.
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