Convertible Top Pump Fluid?? 1963 Valiant

Hi folks - new to working on convertible parts...so bear with me.
The pump struggles mightily to raise the convertible top on my 1963 Plymouth Valiant 200 Convertible. Not sure if the pump motor is low on fluid and will check that tomorrow, or top cylinder(s) are shot??
Real question is what did they use back in 1963 for fluid?? Transmission fluid or Brake Fluid??
Thanks