Thank you, Zoë, you explained perfectly what I was aiming at! It's been years since I've done any of that (more like decades). I do remember with ceramics there are specific stains for achieving that look, not just another shade of paint. It's probably different depending on the material you're painting.
Looking at the original better, it looks like a chip at the upper left side. If it were me, that would be the only part I'd touch up to match the rest. I really do like the look of it as is with the old patina to it.
