Vintage Longines watches have a 6 to 8 digit sequential serial number on their movements. As there is plenty of information about watches from various dates around online it is possible to roughly date a Longines watch by comparing to known dated serial numbers. This tool will work for all Longines made between 1899 and 1980, after that date I have no information as yet. I have estimated dates for years where I couldn't find any information so please consider this a guide only, it should be within a couple of years either way. Please be sure you are entering the number etched directly on the movement itself, NOT the case.