Good info on UK plates but I'm afraid the year identifier on the number plates is probably only for the benefit of police and number plate year 'snobs' (which seem almost unique to UK).
In Germany for instance you get the same number plate every year, and the new plate is endorsed with road tax and insurance details - that seems a much better idea than our year ID, which is hated by motor vehicle manufacturers and garages alike because it causes two artificial 'humps' in the sales figures as everyone rushes to get latest year reg on March 1st and September 1st - it used to be worse when we had only one change of letter per year because that caused one horrendously large sales peak and then very little for rest of the year - no wonder our home car industry had such a hard time.