Well the counterstamp counts as damage, so it's worth face value unless you find someone who collects these things. In that case, I'd guess under a buck, but you should check
ebay sold prices for other states (if Colorado) doesn't happen to pop up to get a better idea.
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz