Use a Breitling serial number to find date and specs
Breitling have used several serial number formats over the years. A simple 6 or 7 digit sequential serial number up until 1979 and then a 6 or 8 character serial starting with a letter (which denotes the material used). The 8 digit version can also be combined with a dial code which is a further 3 digits, separated from the serial using a slash. The earlier number only serials can be used to date the Breitling watch but all the later ones cannot without contacting Breitling. They do reveal other information though.
Note that number only serial numbers differ on the chronographe models so you must set that below. Chronographe models will have "chronographe" written on the caseback.