Monroe F
Another surprise find, on a French second hand site, after some encouragement of a fellow collector. I (and he) had suspected a square-cased Monroe to be a model G, but it turns out the serial number starts with F, dating it to 1917-1919. The main difference between the very earliest models of Monroe is that in the later D, E, F, G, ... the gears associated with the main crank are not enclosed in the very first model(s?), but in this one clearly they are. The machine, apart from the colouring and the decal, is identical to the model that is found in the Smithsonian National Museum of American History. In this one the keyboard top plate is green, with red and green comma indicator strips - the MAH machine has a black top plate and black and white comma indicators.What the exact difference is between a model F and the later G (s/n up to 20.000) remains obscure - their outwards appearance is identical, except for the lifting handle, which could be either a steel strip on the left as in the Smithsonian's model F, or a bakelite knob on the right, for which the foundation seems to be present on my machine. AFter acquiring a Monroe G, it is, however, clear what the difference is. In the model F, the carriage is not yet self-lifting while clearing, whereas in the model G, it is, making the clearing operation much more simple, and one-handed.
The difference between E and F are more remarkable - the material and size of the handles, as well as the clearing key, which is a still red key at the bottom of the keyboard instead of up and to the right. In the model E, instead of a fixed comb with one sizeable tooth on the carriage for locating it, there is a row of teeth, and only one slot mounted on the top right of the keyboard. Also, there are different comma indicator strips on the carriage.
The model D looks for all practical purpose exactly like the model E - except that the Smithsonian also has a model D which looks like a much later machine, and for all practical purposes like my model F. One has to wonder about the serial numbers... The earlier model D seems to be missing the strips between the keys as comma indicators.
A list of machines in the Smithsonian (because their search function doesn't always work well):
The information from the Smithsonian (J. H. McCarthy, The American Digest of Business Machines, Chicago: American Exchange Service, 1924, pp. 80–81, 551), puts the cutoff on model D-E at 4000, E-F around 6000 and F-G slightly over 20000. Whether there has been a model A, B and C remains unclear.
My machine has a very odd decal, which seems to have been (over ?)painted by hand. At least they did use gold paint! Also, it is missing either the handhold for lifing on the lefthand side of the carriage, or the knob on the right hand side. In this model, the carriage does not yet lift itself when clearing. Otherwise, the machine functions just like the later model, with the one difference that the main crank has two rest positions, indicated by the steel buttons sticking out the side of the machine. The top one is for addition, the bottom one for subtraction. There is a "dead" half-turn in between.
Serial number:
Detail under carriage:
Check out the pictures of the "biquinary" stepped cogwheels that make up the mechanism - a 5-toothed sector on the left, and a four-teeth gear on the right with varying tooth length, on either side of each intermediate gear.
