JUVENIA ARITHMO CALCULATOR WATCH CATALOG, CA. 1945

A very rare Juvenia Arithmo catalog/instruction manual.

 The Juvenia Arithmo, introduced in 1945, is a true watchmaking icon that established itself as one of the very first calculator watches in history, long before the advent of electronic technology. The result of a patent filed in 1944 by Swiss electrical engineer Gérald Francis Wittgenstein, this timepiece is not a chronograph but a three-hand watch fully optimized for scientific calculations. 

Originally designed for postwar engineers, pilots, and mathematicians, it features three distinct circular logarithmic scales. The first is fixed and printed on the outer edge of the dial; the second is movable on an internal disc attached to the bezel; and the third is engraved directly onto the steel portion of the bidirectional outer bezel. By rotating this bezel, the user aligns the indices to instantly solve proportionality equations (A/B=C/D), multiplications, divisions, or complex trigonometric calculations, right on the wrist.

The true masterpiece of this piece lies in its optical architecture and its double-dome Plexiglas, dubbed the “Réfrascope.” Its structural design is unique: the centrally located, classically domed section remains completely stationary to protect the hour hands, while a raised, “doughnut”-shaped Plexiglas ring surrounds this center and rotates in unison with the outer bezel. This asymmetrical design acts as a magnifying optical lens, engineered to correct distortion and enlarge the minute scientific graduations, particularly at the critical 12 o’clock mark. This technological feat ensures ultra-precise readability despite the dial’s limited space, lending the watch unparalleled historical significance and visual appeal.

Beneath the dial, the manufacturer has opted for a robust and proven mechanical movement to power its precision timepiece. The main series is powered by the AS 1180 caliber (based on the Adolf Schild movement), a hand-wound mechanical movement with 17 jewels beating at 18,000 vibrations per hour, modified to incorporate a direct-drive central seconds hand. In the 1950s, rarer automatic versions were introduced, equipped with a “bumper” movement, the AS 1250 caliber. Finally, the 36-mm case, made primarily of stainless steel, features a highly distinctive flattened disc shape: the winding crown is semi-recessed at the 3 o’clock position to preserve the perfect circular line of the middle, while the “teardrop”-shaped lugs slope sharply downward to ensure ideal ergonomics. 

The mention of “Bassin & Maillefer” on the back cover of this catalog, No. 100, is a valuable marker of history and authenticity. Far from being a mere detail, it refers to the prestigious Swiss printing house based in Romainmôtier, in the canton of Vaud, which specialized in high-precision technical and advertising publishing in the mid-20th century. This copy is an Italian edition. This very rare manual has a few tears and pages that are damaged in places.

This copy is an Italian edition. This very rare manual has a few tears and pages damaged by moisture throughout.

Publisher: Juvenia
Year of publication: Circa 1945
Number of pages: 22 pages
Dimensions: Height 18 cm, Width 13.5 cm