Hi all, been researching this watch on the net and haven't found anything relevant yet. This is my 4th Heuer and I am looking for information on it's authenticity. The maker's mark is different for the standard Ed.Heuer and the Co has the o in the C. I figure it dates to the late 1910's to early 20's. After posting on other sites I was directed here as the most likely place for information, any help positive or negative would be appreciated.