I've used a spray paint called "appliance epoxy" for the rims, found it at Home Despot, likely available elsewehre. Comes in white, black and off-white. I think the off-white is a decent match for the Schwinn color. Seemed to be more durable than regular paint. It's very particular about the re-coat window however, do it at the wrong interval and it does bad things, ask me how I know.
As the the OP's rim. Yeah, it's a '48 S-2. Stamped but no knurls.
Cheers, Geoff