It's a mule shoe, possibly for front, probably for a rear foot. I've shod a lot of mules with the heels sticking out on a front foot. If that was done on a horse, he would step on the
extended shoe with his hind foot and either pull the front shoe, or get in a worse wreck, but that didn't happen with any of the mules I shod. The shoe you found has both toe and
heel caulks, pronounced "corks." The front caulk is also called a "toe grab." They are on the shoe to provide traction usually in mud or soft ground, while more pointed caulks are
used on ice. Toe clips are drawn by the blacksmith on the hoof side of the shoe, and are then burned into the hoof wall. Besides toe clips, there are also side clips. Clips are used
to take the strain off the nails.
View attachment 1087789
This picture shows a toe clip that has been burned into the hoof wall.
View attachment 1087790This shows toe and heel caulks. This is the ground side of the shoe.