It sounds like you have the so-called Mickey Mouse pickups, which despite the name, are highly regarded. (I have not owned them, so I can't comment personally.)
I vaguely remember something about 'extra' caps in some instruments with those pickups. Maybe someone else can confirm something (perhaps that I am an idiot) but I seem to remember that in some cases there were small caps installed to kill off high frequencies.
In either case (me being a genius or me being a dolt) those ceramic disk caps are extra. If you're happy with the way the instrument sounds, then don't worry about them.
If you're curious what the hieroglyphics mean:
10% tolerance on the capacitance
1KV voltage rating. 1000 volts!!
1500 picofarads
Z5F temperature coefficient. It specifies how much the capacitance can (will) change with temperature. Not really important in this application.
And, to add a useless but interesting data point, this thread reminded me that I still have what I think is the original wiring harness from my '58 T-100. I dug it out and measured the pots. The volume measures 890k and the tone measures 830k. WTF? I know they can creep up with time and use, but that's a long way from 500k, which I might expect. (Single Franz neck pickup.)
Oh, and the cap is a 0.05uF red Astron.