1950s Arithmo Slide Rule Steel

A rare and highly intriguing vintage Juvenia Arithmo Slide Rule watch from the 1950s, presented in exceptional condition and appearing unpolished. Introduced by Juvenia as the “first calculating watch that shows time and solves your problems,” this innovative timepiece was designed with engineers and mathematically inclined minds in mind, with its original instructional booklet detailing a range of practical operations.

The defining feature is its circular slide rule, operated via the outer rotating bezel—referred to by Juvenia as the slide index—crafted from what the brand described as “unbreakable glass.” The bezel rotates bidirectionally, while the inner scale remains fixed, allowing various calculations to be performed directly on the wrist. The distinctive donut-shaped crystal, paired with the domed bezel and dial, contributes to its substantial 12mm profile.

The lightly patinated silvered dial is accented by gold-toned Arabic numerals and baton hour markers that catch the light beautifully, complemented by matching gold-toned hands. A black dotted minute track adds contrast and legibility. Despite its 34mm case width, the Arithmo wears with notable presence, its unusual slide rule complication serving as both a functional tool and a compelling conversation piece.

Fitted with what appears to be its original leather strap and unsigned buckle, and accompanied by the original Juvenia instructional booklet—a particularly nice addition for a watch whose unusual functionality is such an important part of its character.