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Comments

Ray Girvan

The Rechnerlexicon has full PDFs of this patent, as well as the one for its earlier incarnation coinvented with Fletcher W. Potts:

http://www.rechnerlexikon.de/files/patent/US180949.pdf

http://www.rechnerlexikon.de/files/patent/US175775.pdf

The Adding Pencil Co. of St Louis, MO, was still selling them through ads in Popular Science and Popular Mechanics in the mid-1920s. For instance: http://tinyurl.com/kv4eks

Jeff

Am I mis-reading or is the Adding Pencil Co. ad misleading? It seems to be claiming that all you do is press the pencil tip on some numbers and it adds them automatically. Must one behave like a counting horse and press the tip nine times for "nine"? Then it continues and says that it adds as you write. This is all different, I think, from the claims in the patents above. Would've been a late-night TV ad, if they'd had TVs.

Ray Girvan

The one in the ad looks as if it operates in a different way from the dial-twist of the 1876 one. The graduations near the tip suggest that to add x, you push down until the tip slides into the body of the pen by x notches, and x is added to the total (after which presumably the tip disengages and springs back ready for the next input).

If you zoom in on this other ad in Popular Science - http://tinyurl.com/ls2vgb - you can see the graduations are numbered consistently with this.

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