!Need Help! with compressor part.

I have acquired a vintage air compressor that runs so much better and quiter than my newer Craftsman, I decided to keep it. It has not been well card for, and I need to change the oil. There is no oil plug, only this glass cylinder mounted atop a home-made stem. There is only a valve on the top like a bicycle tire valve. It seals up but has a small air hole in the top. It's made by Jacuzzi and it's called a "super charger". I would greatly appreciate if someone can tell me what it is, how to use it. Logically thinking, it seems like it should mount lower to reflect teh oil level in the housing but that doesn't explain the pressure valve.

I did almost exactly that. I used some pipe to extend the mechanics and give myself a fill tube. Although I re-
mounted the device. Any idea how much oil this thing should take? I dumped out almost 2/3 of a quart. Do old compressor pumps have oil pumps inside? Or do they bathe in oil. I added one quart and it still knocked a little bit after it ran for a while. I put in a second quart and it all seems fine. That seems like an awful lot of oil. Any input?

• Photo of compressor pump