In 1950 Rolex needed an automatic movement for their budget brand Tudor, the solution was to modify a EFE calibre 380 to feature an autowinder mechanism. This movement was baptised calibre 390. Rolex also modified the movement further fitting a date mechanism: calibre 395. There are many design similarities with Rolex’s own in-house calibre 1030. Especially when you look at the clips that hold the reverser wheel and oscillating weight in place and the design of the date mechanism, but unlike the other Rolex design; this one has a bad habit of eating itself. There are a lot of collectors that are eager to snap up a nice Tudor featuring a calibre 390, but good luck finding a watchmaker happy to work on one. I hope to never see one on my bench ever again;)
Click on the link below to see the movement review.