Holy crap. What a complete handyman-special joke this thing is. Unreal that he's actually sold some of these. To people with working games, no doubt! (from the auction: *** Item is intended to replace the power supply system in a Fully Functional Machine ***)
Only running a single conductor for each voltage, fusing switcher outputs, having an entire outlet box for a wall-wart from an alarm system or whatever he's got there when he should just screw a standard transformer onto his super-sweet mounting board system™.
It is sorta what you'll end up with if you do this yourself, but that's the point of doing this yourself: you can build this for ~$150 and probably do a better job. I personally dislike the switcher kits and only run 125VA supplies in MCR (WMS games get switchers!), and I've ripped rigs like this out of games to replace with OG even recently, but they'll work fine for the most part and you can mod the adapter board if you have hum on the audio.
The oil-filled cap is for the ferroresonant transformer. It's a simple circuit that self-regulates line-voltage - I think I did a post explaining it a few years ago if you search, but the short version is that it's completely unnecessary. As long as you get the correct voltages out of your transformer, you won't need the oil cap. Nothing you'll run across will need one.
The automatic line-voltage regulation is a pretty great feature of MCR games, but it's also completely pointless if you're using a switcher. You get to ditch the transformer, the oil cap and computer-grade caps when you run a switcher.