Hi ,

I have just finished to refresh my new CK 374, the model that was created by Omega in 1934 to commemorate the 40th birthday of the brand (I already had one which I already posted here, but with a hairline on the dial, this one is in better condition) :



The watch has a 38.5 LT1 Inside. On one of the plate there are two markings : a quite classical 'M' which, I think, means t was in a metal case, but also the three letters 'EXP.' which I don't remember having seen before. Does anyone know what it stands for?