Yes, you have a 1985 T-1550. They put tags near the entry door on later models, starting around 1988/89, but yours is too early for it. Your coach originally had a sticker on the street side front that said the VIN and model number. Chances are that sticker is just a shadow now, based on how faded the rest of the trailer looks. The stickers didn't hold up well at all.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9473.8 (as of 6/18/21)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR