A Watch That Can Calculate? 1940s Juvenia Arithmo

---

 A rare side-by-side comparison of two iconic Juvenia Arithmo models from the circa 1940s–1950s. 📐⏱️ 

First introduced in 1945, the Arithmo became famous for its rotating slide rule bezel. Shown here are two distinct mechanical variations from that era:

👈 Left: Bumper automatic movement in a 36mm case, with Roman numerals paired on a beads-of-rice steel bracelet.

👉 Right: Manual-wind movement in a 35mm case, featuring classic Arabic numerals on a black leather strap.