Here is a demonstration video to help you determine what
Mesa Boogie Dual Recto that you have. Is your Recto Revision C, D, E, F, or G? We know REV C and D are pre500 (up to R-0503). And pre1000 also use MKIII (Mark III) OT and Choke Transformers... what Recto do you have?
http://www.youtube.com/watch?v=c_5qFMT5ghM