Amongst many vintage watch enthusiasts, Omega has a strong hold both aesthetically, and because of the mechanical innovations made by the brand. One of these is the calibre 28.10. Introduced in 1943, it was Omega’s first commercialised automatic moment, and is considered to be one of Omega’s legendary calibres.
The term “bumper” refers to the automatic winding movements from Omega (but not exclusive to the brand) which were very popular in the from the 1930 to 1950s.
When the weighted hammer to wind the mainspring (swinging in a pendulum fashion) reaches the end of the distance it can travel it bumps into a spring and stops. This bumping can be felt by the person wearing the watch, thus these watches are often referred to as “bumper automatics”. Beginning with the 28.10, the “bumpers” went through to the cal.355.
This is a 1946 (10M service number) 18kt solid gold Omega with bumper automatic movement Calibre 28.10. There is a watch identical to this one in the Omegamania catalogue, called the “Ambassador” model.
This as-pristine-as-you’ll-ever-find-a-watch-from-1946 was purchased from the original owner with case, movement and dial in amazing condition and totally untouched, which is quite rare for this age of watch. Bumpers may be fairly easy to get, but ones of this vintage and this little worn, are not.
The calibre 28.10 was renamed cal.340 in 1949 and became the basis of of the cal 34x and 35x bumper movement. There were different iteration of the 20.10, with 28.10 SC being the centre second. Calibre 28.10 was unidirectional wind whereas the cal 34x and 35x had bi-directional wind. Interestingly, the cal.35x had a swan-neck regulator not found on the calibre 28.10 or cal.34x, and I believe these swan neck regulator movements were certified chronometres.
A prototype self-winding rose-gilt movement with triple-calendar developed in 1944/ 1945 but never commercialised. This movement was based on calibre 28.10 (340). Had production of this movement gone ahead it would have been the world’s first automatic wristwatch with triple-calendar.
Apart from being used in the vintage automatic line, the first Constellation in 1952 also used the 28.10 movement.