RV2. I presume that the previous owners did not keep the original documents and manuals on the trailer. Holiday Rambler was purchased by Monaco which went bankrupt last year and was purchased by Navstar. Contact Monaco and see if them can supply some information on the trailer.
Otherwise, the wiring on brakes and lights is pretty standard for trailers and you might get some help from a book like RVing for Dummies.
Amateur Radio Operator (KE5DFR)|Full-Time! - 2012 6.7L Ford Crew Cab Dually -2013 HitchHiker Champagne 38RLRSB - Travel with one Standard Schnauzer and one small Timneh African Gray Parrot