The watch dates to 1954 and the case dimensions are 36mm in diameter and 41mm lug-to-lug. This is a great vintage watch that still fits the modern wrist very well. The nickname for the watch is "Disco Volante," or flying saucer because of the thick steppe...
One more bit of info is that the case was made by Wenger . Also made cases for ref 2499 The code or stamp or chop in the case back is a key with a number 1 Julian