The original Radiomir watch— named after the luminous material patented by Panerai to make its dials legible in the dark — debuted in 1936, with a case whose lugs were made of strong, bent pieces of steel wire welded to the case. For the 1940 upgrade, Panerai created a new case with much larger and more solid lugs, milled from the same block of steel as the case. The new version also had a more secure system for attaching the leather strap to the watch: where it had previously been necessary to sew the leather around the wire attachments, the new construction added small holes in the lugs into which small tubes could be fitted and inserted through loops at the ends of the strap. The revisions to the Radiomir case also included softer edges on the cushion-shaped curves, a larger and more cylindrical winding crown, and a thicker overall profile (15 mm to 17 mm).
The modern case of the Radiomir 1940 3 Days Oro Rosso (PAM00515) is slightly thinner but still large (at 47 mm in diameter) and made of polished 18k 5N rose gold, an alloy with a high percentage of copper and a bit of platinum. It has a polished bezel, a screw-down crown with the historical Panerai “OP” emblem, and 1.4-mm-thick corundum sapphire crystals in the front and back, treated with nonreflective coating.
The dark brown dial, with small seconds subdial at 9 o’clock and date window at 3 0′clock, is constructed in Panerai’s “sandwich” style, comprised of two superimposed plates with a layer of luminous material between them, a Panerai innovation dating to the late 1930s.
The movement is Panerai’s manual-wound Caliber P.3000, developed and produced entirely at its manufacture in Neuchatel, Switzerland, which boasts the three-day power reserve that lends the model its name. The movement, visible through the exhibition caseback, achieves its lengthy power reserve by means of two spring barrels in a series. It has wide brush-finished bridges with chamfered edges and a variable inertia balance with an extra-large balance wheel (13.2 mm diameter), oscillating at a frequency of 3 hz. Caliber P.3000 is also equipped with a device that enables the hour hand to be adjusted in jumps of one hour either forward or backward.
The Panerai Radiomir 1940 3 Days Oro Rosso comes on a brown alligator leather strap with a polished rose-gold buckle. Panerai also offers a version in a stainless steel case (PAM00514) and two Radiomir 1940 models in 42-mm cases in steel (PAM00512) or rose gold (PAM00513), containing Panerai Caliber P.999.