ROLEX MARCONI JUMP HOUR AS340 1920s
Adolf Schild (AS) was a major manufacturer of movements in the XXth century (now ETA) that were fitted to hundreds of different brands both private and "in-house". The round AS340 digital jump hour calibre is probably the most popular of all and even the Rolex Marconi watches housed these movements in sterling silver or solid gold cases. The watch pictured here is not exactly a Rolex but there is absolutely no difference so why pay more for the same thing especially that this one is far nicer due to the art-deco pattern on the nickel-chrome case. The movement shown is the highest grade available from AS with 15 jewels, fancy individual bridges, gilded gears and three adjustments. I have seen Marconi watches with lower quality than this :)
The base calibre movement can be found in standard analog watches so you can easily replace the mechanical parts. The main difference is an additional post on the baseplate that holds the hour disc and corresponding screw. The minute disc is factory press-fitted onto a standard cannon pinion and installed onto the center wheel pinion. The minute disc has a small finger (at 30) which turns a gear on the hour disc when the minutes reach 60. The main issue with these movements results from a slipping (worn-out) cannon pinion that can not transmit enough torque to move the hour disc. Tightening the pinion is a pain and rarely pays off but as shown you can punch out the disc from a brass post and afterwards remove the post from the cannon pinion. This is difficult due to a very tight fit and results in certain damage to disc and post.
In order to create a proper jumping function a tension spring is installed on the left that allows the hour disc to jump by only one hour. These springs are very often broken but you can create a replacement from scratch and adjust the jumping functionality by trial and error. I suggest using a thick hairspring from an old clock and bend it properly as shown to the left. PS. If you have some spare discs and an analog AS340 movement you can try to create your own jump hour with some additional DIY :) PS. Due to the robust case design with small windows these watches could withstand heavy wear and were thus marketed as the optimal polo and sports watches :))
Keywords: rolex marconi jump hour, schild jump hour, deco jump hour
Market value: 75-500$ (non-brand, Marconi brand, condition)