All they have to do is look at the license plate, and they will know (assuming they know anything about Montana license plates!) that the rig is 11 years old or older. It has PERMANENT license tabs, which are only available for motor vehicles 11 years old or older.
If the Rv park management questions the age of the rig, well, y'know, one of the benefits of being on wheels is I can get on down the road real quick!
And I will.
I have never had the question asked. Not in Montana, Wyoming, or Idaho, and not in any RV park from Montana to Georgia and back.