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Manufacturing Dates for Burroughs Portable Adding Machines The Burroughs Portable Adding Machine introduced in 1925 became the basic design for the adding machine for many years, until the ten key adder was introduced and started to replace it gradually. Determining the data a Portable Adder was made is difficult because serial number to date tables are difficult if not impossible to find. There are a number of construction changes that do help to identify an approximate date range as shown below. Portable Introduced - 1925 - Class 8. The basic adder was black in color with a green keyboard base plate. It had round keytops and did NOT have subtract capability. It used an all black ribbon, and was first released in hand operated models only. The case of the machine is secured in the front with a single screw. First Subtract Design - 1928 - Class 9. The Portable now had subtract capability. The first subtract mechanism was a metal lever which came through the keyboard to plate in the lower right corner of the keyboard. The level was pushed toward the top of the keyboard to set up a subtract operation. First Electric Design - 1930 - Class 8, 9, 10. The Portable became available in both the traditional hand operated model and now an electric model. The machine came with a handle (just in case). First Two Total Design - 1930 - Class 10. The Portable adder now included a new model, the Class 10 machine. The primary difference was the addition of a second totaling register. These machines became very popular as "teller" machines in banks. Many models were made over the years. They were normally built with many features needed by banks such as locked paper rewind, check or receipt printing capability, numbering features, multiple totals, rotary date stamp feature, keyboard protection column covers, etc. New Subtract Design - 1934 - Class 9. In about 1934, the level subtract design was changed to a large key on the right edge of the keyboard. Army Colors - 1941 - Class 8, 9. During the war years the machines were first painted a khaki color at first and later an army green. Square Keytop Design - 1945. The traditional round keytops were replaced with more modern style square keys and the color of the machines changed from black to a dark brown with a rough finish. New Light Colors - 1949. The color of the Portable changed to a light brown color about this time. New Case Design - 1954. The case of the portable was completely changed to a smooth rounded case. |
