Until 1964 , most Trixon kits left the factory with calf heads. Those that were fitted with mylar heads, had the original Ambassadors on them-----double ply, until ambassadors were changed to single ply heads, which Trixon continued to use.
I have 6 different custom made Remo formulations for for the old pre-64 TRixon metric drums( snare, 363 mm, floortom 426mm and 363mm and bass drums 500 and 550mm are the only affected drums----the rack toms almost always will take a 13" head), To get the drums to play the way they they would have originally, the Vintage Ambassadors seem to be best on the 363mm snare, coupled with an ambassador hazy; the Ambassador Rennaissance seems best for the 426 mm floor toms, Fibreskyn III for the 363 and due to the superb muffling latitude of all the Trixon bass drums, those heads can be more open and vibrant, with lots of choice to meet personal taste there.They really shine with a heavy calf on the batter and goat on the reso.