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 – 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)

This appears to be what is known as a "Triple Section Electrolytic Capacitor" which seems to be a fairly apt name.

The three legs have symbol stamped into them which correspond to each of the three markings on the capacitor. The shell is presumably then connected as the common terminal.

Essentially it appears to be three capacitors wired up in a Wye configuration, each 50uF in capacitance. Two are rated for 400V, and the third rated for 350V. Although the third one having a different rating seems to be weird.

It is a twist lock multi section capacitor.

Seldom designed into new equipment but pretty common in still functioning and restored valve (audio) gear.

You could try and see if your circuit could cope with one of the replacement types from TEDSS or from Amplified Parts, failing which you could insert 3 x 50uf 400V contemporary radial electrolytic capacitors under the chassis or into the gutted old can.

The can will be the common negative terminal.