Before 1987 - Serial number consisted of between 5 to 7 digits.
1987 - Rolex added a letter at the beginning of a serial number that consisted in 6 digits.
2005- Rolex started engraving the cases serial number on the inside edge of the case at the 6 o'clock position.
2010- Rolex began engraving its watches by using randomized identifying numbers rather than using a sequence numbering system.
At the present time, Rolex features 8 digits instead of 7 digits.
