It can indeed be tricky because identification has changed a number of times since Paiste first introduced serial numbers in 1972/1973. It also applies primarily only to their Swiss made cymbals and not their German made ones.
The “PAISTE [SERIES]” stamp over a 6-digit serial number was used circa 1981-1986 and the first digit of the serial number indicated the last digit of the year. Thus, your cymbal would be a 1981.
If you or anyone else would like more info, there are a couple of decent resources on the web to keep things straight... like this one at cymbal wiki: