You should bother 😉
You can't have a nice looking amp like that with no working power indicator.
(As you were up to contact cleaning you must be up to sorting that out too).
According to the service manual, it's an 8volt, 50 milliamp filament bulb.
If you're bothered (make sure you are 👍) AND TRUST YOURSELF TO AVOID LIVE MAINS get a multimeter and look for a low AC voltage on the bulb holder.
If it's there, you just need a new bulb - if you can't find an 8v bulb, go higher rather than lower.
(An LED replacement would be better - but you'd need a type with built-in rectification to cater for the AC).
Amp came back in much better technical shape.
summary of everything since I got it
-cleaned it up
- Fresh black coating has been applied to the top cover.
- changed the binding posts to modern ones
- added jumpers to the binding posts. Speaker 1 or 2 provide 4 ohm each, Speaker 1&2 together is 8 ohm.
- technical revision solved the crackling noise
- indicator light now works.