Honestly, I'm not sure how they did it. The invoice on the Grand Record (which was done by Forever Powder Coating in Olympia) gave me the impression that they might have just painted the lugs, but I've since had a Grand Jubilé powder coated by Groody Bros, and I know they used powder because I placed the order for the powder and had it shipped to them.
So, I know it can be done, but I don't know how. I've heard that it involves some kind of specialized high temperature tolerant masking.