classic parts

How can I tell which classic model I have? Check the serial number - it usually looks something like: GK 0312/0123B/12345. The first four digits after the two letters represent the month and the year. 

classic v1 (only in red): serial numbers 0208 - 0510

classic v2: serial numbers 0610 - current

classic twin: serial numbers 0208 - 0909