I have seen only one other kettle bowl that was similar but it was devoid of all the porcelain. It had been used as a fire pit for many years at a beach house. Interesting how that ring of remaining porcelain is consistent with how the bowl set into the table. If only it could talk.
I would think using a rust remover such as Loctite Naval Jelly will remove the rust. Once you get the rust removed, I would season it with cooking or olive oil and put it back into use. I have never tried priming, painting, then cooking on it after painting. If you used a high temp black paint, it might not show the darkening problem that others have complained of that have tried painting one. I'm interested in hearing others suggestions.
I confused who secured what grill. Congratulations to Charlie on the Woodard and congratulations to Ritesh on the never used redhead.