Welcome to the site. We also have an older unit, a 1982 Sunline 15.5 SB that we've used for the last two years, doing a complete loop of the USA and a trip to Labrador.
We've loved it. We purchased it from the original owner and like your's he had the original paperwork.
Interestingly for us, people frequently ask us if we want to sell. Apparantly these little rally light units are not being manufactured, though I've noted they're making a comeback.
Have fun and safe travels,
Norm and Ginny Milliard
1982 Sunline 15.5 SB
2004 Honda CRV 4 cyl, manual