Movement Serial Number Lookup

There does not seem to be any accurate publicly available data from at least 1969 to 1974 as well as after 1980. Some datasets do claim to give accurate data up to 1980 though from my testing I believe that these data sets will claim any numbers between 15,000,000 and 50,000,000 is from the year 1969 and I am not sure what the source for their 1974-1980 data is. In 1969/1970 Longines began to number movements in a new series that started at 50,000,000. Interestingly, when getting an extract from the Longines archives for a watch that starts in the serial number 50,000,000 range, the extract will come back noting the case and not the movement serial number. These case serial numbers appear to follow the original series (though there are some inconsistencies especially in the years 1969 and 1970). For a truly accurate determination of the age of a watch in this grey area, I strongly recommend you get an extract from the archives.