Assuming it came from the factory with the bail, it is a 46-48, which takes a two piece "rabbits ear" cap.
You can buy an inexpensive kit to delete the bail and fit spring clips to use the more popular 41 style "crab" cap. The crab uses a different rotor than the later rabbits ear two piece cap.
So just get a cap and rotor for a 41 and the spring clip kit and you're good to go.
Mart.
Edit: Read Macs note below - I goofed on the years!