How do I know if I have a B5 or a B5.5?

[audiohertz]

This might seem a little lame and I'm sorry if this offends any of you, but I'm new to Passats. Just bought one to replace my BMW as the costs are less than half price to run each month! It's a 2001 Passat, but how can I tell whether it's a B5 or a B5.5?

Any help would be appreciated.

Thanks

Adam