It doesn't go for as much as coal, but old NPC armor and especially armor made from old smelted NPC ingots can go for quite a bit. This stratics
colored plate page shows the various colors it was possible to get, so you can match up the hues you have if you want.
The weapons of exceptional quality, I'm gonna guess they have 20% DI on em. Theres not really a lot of value to such pieces, as there is still a lot floating around, tho less than armor of exceptional quality as that stuff is more useful than the old weapons usually and people won't toss it if they can use it. I hold onto a few old 20% DI pieces made by my crafter for nostalgia. I really don't think it's worth much otherwise, but I could be wrong.