I know its next to impossible to date a horseshoe... But I found this horseshoe in areas where I've found other old items.... It is smaller compared to any other horseshoe I've found before... Smaller than a mule shoe or a regular size horseshoe... Is this for a baby horse..? No idea..
Like the above posts say - probably a pony shoe. I've found a few but they don't appear to be as thick and heavy as your find. Pony carriages were fairly common around here.
HH
dts