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Stephenson Adder


Stephenson Adder Copyright March 27 1873

Stephenson Adder Calculator. One of the first calculation devices was the Stephenson Adder, billed as one of the first pocket sized calculators put into mass production. In fact, the original model (the one involved in the patenting, number 137107) is in the Smithsonian, and is on display along with other calculators of its age. In 1873, said patent was issued, its invention accreditted to Archibald Stephenson. Many of the more costly versions were Nickel plated. However, there was a second, non-nickel plated, cheaper version of the adder. It was designed so that any elongetated item (a pencil, pen, stylus) would be able to successfully manipulate it.

G.N. Mindling Adder Copyright March 27 1926

The adder is built in such a way as to follow addition in a "natural manner". What is meant by this, is that it is built in a way that is taught to kids in elemntary school. It weighs less than a pocket watch. The Stephenson Adder was quite cheap, compared to the other versions at the time (The Webb adder was 6$, about 2 weeks wages for many citizens at the time) However, due to its compact construction, there is no straightforward method in cleaning a Stephenson adder. Image source Ebay post from New begin-antiques.

C.B Simmons Gen'L Agent Oil City.

A specific model of Type 1 Stephenson adders made in Oil City, Pennyslvania are instead marked by the name C.B. Simmons. Source: I found this picture on an Ebay post.

Brevete Mon Ami French Pocket Adder Source: Ebay

For more information on Stephenson Adders visit this site.

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