Well I'm afraid it's not quite as straight forward as that. Yes you can date your van by some of the parts fitted like fridge, cooker, heater and cassette loo, as all these carry an individual manufacturers serial number and often carry the month/year of manufacture.
I came across an anomilyin 2008, when looking for my current van. We saw a Fleetwood Nocturne Sonata at P Briggs in Gloucester for what seemed a very good 10K price tag for a new van. Apparently, it had been "lost in production" at Fleetwood for 2 years !! PB were selling it as a discounted new van because it had no previous owner but was 2 years old. It also carried a 2008 VIN plate and had no CRIS regestration. The caravan was actually made in 2006.
Needless to say, apart from the interior looking like a swedish sauna, we gave it a wide berth and went for our then 3year old Abbey Frestyle that was onsale at their cinderford depot. It may well of been a genuine van and someone would love it, but as it was being sold with a 2 year reduced guarantee, we felt there were too many chances of there being trouble with insurance and resale value to take the risk.
Another thing crossed my mind. That was, if you can get "cut and shut" or "cloned" cars and also re-registered total loss cars carying a new regestration consumate with the year of manufacture, then the same is possable for a caravan. You only have to look at flea bay to find blank trailer ID & weight plates available for the price of a pint.