Panerai:

The special design of the Luminor 1950 case used by the two models is inspired by a rare, historic watch which is notable for the pronounced rounding of the cusps of the caseband. This  detail recalls a stage of transformation, which took place in the 1940s, from the classic Radiomir cushion case to that of the Luminor.

The Luminor Marina 1950 3 Days and the Luminor 1950 3 Days Power Reserve are both fitted with the new P.3001 and P.3002 manufacture calibres, which are distinguished from each other by the different ways in which the power reserves is indicated. In the P.3001 the power reserve indication is located on the bridge of the movement, and is therefore visible through the crystal on the back, while in the P.3002 the indicator appears on the dial. With a diameter of 16½ lignes, the two calibres have in common the typical structure of large bridges, two spring barrels giving a power reserve of three days and a balance wheel 13.2 mm in diameter with variable inertia, enabling the rate of the watch to be adjusted through external screws on the rim. Both also have the seconds zero reset device and a mechanism for the rapid adjustment of the hour,
enabling the hour hand to jump one hour at a time, without interfering with the movement of the minute hand or the running of the watch.

Panerai Luminor Marina 1950 3 Days (PAM 423)

47mm steel case, manual-wind Panerai P.3002

Functions: hours, minutes, seconds, power reserve indicator, seconds reset

Water resistance: 100 metres

Crystal: Crystal 3.0 mm