The date serial number is usually on the end of the bench on the bed extender in a Puck, I had a good bit of good info from Jandi which helped me to pin my previous Pucks date down, generally the Eribas serial number starts with a 5 for a 1980's and a 6 for a 1990's the next number after it is the year, i.e. serial number starting with a 63 such as my old puck was a 1993. It's not an exact science as the French Eriba seemed to have no continuity with their numbering system.