At least if you are going to believe the Omega advertisement in 1948! "Une montre unique au Monde" - "A unique watch in the World"! Omega Centenary - The 100 Year Anniversary watch of Omega: Last weekend we had the "Most Elegant" WristScan Theme, guess th...
. . . which differed both in case size - 33 vs 35 mm - and movement - 28.10 JUB vs 30.10 JUB. Yours is the latter, I believe. These auto chronometers were so successful commercially that Omega continued producing the ref 2500 with cal 333 movements in the...