the 10 year rule, how common is it and how is it enforced

I've yet to meet a single person that can identify the age, make, model and style of every RV that was ever made. So, when you check in this year, its a 2003 model. Next year, it magically becomes a 2004 model. What's the worst that could happen? They make you prove it, so you move to the next place. I can't imagine any CG owner that would turn away a vintage Airstream. But if it looks like its about to make its last stop...