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          El Calculador!

    What a name! Yes, I know, in Spanish it simply means "The calculator"... but hey, to the untrained ear it sure carries a grand overtone, akin to that of "El Matador", or "El Conquistador"...
El Calculador - front side
    This is one of the numerous calculation aids that have sprung up to fill the simple reckoning needs of the mathematically nave, before electronic calculators became cheap and ubiquitous. Slightly battered but still fully functional, it comes from Spain, where the owner of a small antique shop dug it up for me from the dusty back recesses of his store. He told me he's never seen anything like it, and since I haven't either, I was all too happy to add it to my collection.
    El Calculador is a finger-thick cardboard tube 22 cm long with wooden plugs in both ends. Around the tube is a "cursor", a sliding brown paper tube that can be rotated and moved to any position on the tube. The instructions on the cursor are simple: "Se pone las cifras del tubo junta a las cifras blancas del rodillo. Entonces la resulta es visible en la ventana al otro cabo del tubo." That is, one sets the numbers on the cursor next to the white numbers on the body; the result is then visible in the window at the other end of the cursor.
Sample calculation  Sample calculation
    Admittedly, it took me and the seller a few minutes to figure out which numbers are which... the idea is to juxtapose the numbers with the red background on the two parts so they align to make a complete multiplication exercise, such as "5X9" at the left of the leftmost photo above; the result, 45, is then seen in the window at the right end of the cursor. Meanwhile the "19X18" at the right, in  the same photo, gives the 342 in the left window. The other photo shows the cursor positioned to show that 7X1=7 and 11X20=220. Basically, this is the good ol' multiplication table, rolled up on a tube with a cursor to guide you to the right answer, as long as it's under 19X20.
    The other side of this marvel of mathematical technology can be seen in the photo below.
El Calculador - back side
Exhibit provenance:
    An antique shop in Madrid, close to the Puerta de Toledo.

More info:
    The long-gone manufacturer of this item is identified only as "HABS" D.R.P. ... and I have yet to find any reference to it anywhere. If you know more, please let me know!

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Copyright 2006 N. Zeldes. All rights reserved.