Start by reading this link-https://isrc.ifpi.org/en/ - In the how it works paragraph, roll over the light grey box. Next click the “See the code Syntax for more information” . Read & digest. Now click the “validating ISRC codes”. Read town to “See Country Codes” for a list of countries. Finally have a pint or two. You have just reached the next level of OCD.
Note that, depending on registrant, year is either year of recording or remix (most useful, IMO) or year of registering the ISRC (least interesting, IMO).