Is the number you are quoting the serial number Caroline and does it appear on the plate on the outside of the van adjacent to the bottom of the door?
If so then I agree with Hob. I've always been led to believe that a number starting with 6 means that it's a 1990's van and as the second number is 0 it indicates that the van is a 1990 model.
Likewise, if the number starts with 5 it means it's an '80's van and if the second number is 8 then it's a 1988 van.
However, I wouldn't be too concerned about it. The more I read about Eriba Touring production, the more amazed I get. There appears to be a history of misleading plates fixed to the side of some vans. We discovered earlier this year that the plate on the side of our van suggests that it's a Troll 510 whereas it is in fact, a 530.
Similarly, the more they change hands, the less likely you are of getting the original documentation.
Randa