an 1986 would be a "pre-1500 series" trailer....in or around 1988 there was a marked change in the company and it's offerings/methods. (not that there's anything wrong with "pre-1500s...just different things to look for)
with trailers that are 20 and 30 years old....it's all going to be about visual condition, past maintenance(or not), upgrades on systems and/or running gear over the years.....
a good rule of thimb would be if the seller knows his trailer very well, able to explain/detail everything about it....consider it....if he says something like: "Don't know much about trailers but everything seemed to for me."....walk away....fast (estate sales excepted of course)
there are a lot of BF17s on the Island...but you won't find a lot of them for sale
at the same time...and they don't stay "for sale" long
I'm in Courtenay....PM me if you want