Some kind of earthenware knob . . .
It's 1 9/16" and I haven't seen another like - reminds me of Tigerware. If anyone has any idea what sort of ceramic this is I'd be happy to learn more about it.
I've been tempted to start a thread to see how many of the different color combos we as a community can put together, but I think it'd take a lot of work to keep track of what's posted and I don't have much appetite for trying to herd cats. lol.