I had a YZ250S for enduros, and it was a much better bike in the bush than the 87 model. The '86 just had a magic motor for enduros.. Although I suppose you could have just put an 'S' barrel and pipe on a 'T'..
And Anand & Thomson were getting the 'T''s complianced, so it is a bit strange...
Actually, still have one of those compliance plates sitting in my garage now. 1987 Yamaha YZ250AT.
They never fixed them to the steering head, just gave them to you when you bought the bike. Guy who bought mine only wanted a motocrosser. Only owned the bike for 1 year, but had it registered for another 4, if you get my drift....