2007 Wyoming. the horses tail, is this doubling? If so how rare or common would this be? I hope the pictures are good enough for detail
I don't think so. Probably Mechanical doubling that falls under the worthless doubling category. BTW, true Doubled Die are varieties. They fall under the variety category not the mint error category. There's a difference. So to ask New Error? Would be incorrect.
There are some popular die chip errors for this specific quarter. They are not worth much, but interesting. Some call them, the "pooping horse." If you see one, you'll know why it was called that.
If that’s the only place it shows on the coin then, more than likely, it is die wear/deterioration…imo.
If you go to this Variety Vista page you can see there are 58 Doubled-Die reverse varieties for the 2007-P Wyoming quarter. Only one DDR for the Denver minted quarters. Your quarter is mechanical doubling but, you can search for the other 58. http://varietyvista.com/09c WQ Vol 3 States/DDR Listings.htm