How to identifiy this "2222 063 90025" vintage capacitor?
It's a three section electrolytic capacitor, with the three symbols indicating which pin is associated with each capacitor positive lead. 
The three capacitors share a common negative terminal (the can) which you will observe is grounded by virtue of being bolted to the chassis. I see soldered lugs on the can to reinforce that connection.

Commonly used as the power supply reservoir capacitor in a vacuum tube amplifier.

Note that one section has a lower rated voltage : you'll see it's connected to the others via a high-ish resistance, to provide a well filtered (quiet) supply to the sensitive preamp stages.

Circuitry will be easy to trace out and will look roughly as below...







simulate this circuit &ndash; Schematic created using CircuitLab

If you can't find a replacement, you can use three separete 50uF 450V capacitors. Bonus points for assembling them into a lookalike can... 

(A bit more reading suggests this was a Philips part number)