I had a heavy plastic one like this - same hollow values - as a little kid in the early 60's. Very popular early 60's with popularity of shows like The Lone Ranger, GunSmoke, The Rifleman, Have Gun Will Travel, Bonanza, The Virginian, Wagon Train, Maverick, The Big Valley, etc.
Do the bottoms of the hooves look like they were affixed at some point? This may have simply been what it is...a display item.