Is this a 66 wiper switch?
 

I think it is but wanted to make sure before I advertise it for sale. What would it be worth?

Yes that could be a 66 switch.
A 67 has three terminals for a two speed wiper switch.
The knob is definitely 66.

Looks like a single speed switch. Should have the 3 terminals like Scott said for the 67 2 spped wiper motor. Xs 2 that it's a 66 knob.

What does you're switch harness look like? 2 or 3 female plugs?

That's a 66 2 speed switch, 3 spades.

Here's a better pic of the back. I already have a 67 switch hooked up, just need a knob.
I thought someone could use this one but I don't know what a fair price would be.
I'm guessing less than a million!

Bob is right. I didn't see that 3rd spade. :o