The ETA 2840 is a mechanical watch movement that was developed in 1949. It was the first gents automatic-family movement to feature a ball-bearing rotor. Shortly after its introduction, it was replaced by the 1254UT, which had a different rotor shape. Throughout its production period, there were various modifications made to the movement. These modifications included a change from T- to U shock device and a modified calibre, resulting in many variants of the movement. It is unclear whether all calibres were made in the TC variant, so only the known variants are listed. Some UT versions even had their signatures changed to UC. The ETA 2840 movement includes functions such as automatic winding and a sweep second hand. Further details about its manual winding function can be found in the 1249UC.