It was the burner caps as Sded pointed out; They seemed to be enameled cast iron, but not enameled on the bottom where they would rust until the flame was impeded and I would have to clean out the corrosion. Perhaps by 2003 they were using the brass caps.

The non stainless parts were internal to the stove, I only saw them because I had to dismantle it to replace the broiler element. Do you have a broiler ? That was the most annoying problem.

Cheers, John.