Do you mean Sweetberry? The earliest release G3s had their hoof hearts on the display side, till Hasbro changed that so the hoof heart was on whatever foot the magnet was in. I don't really think they are considered worth any more than the later ones.
Edit:
The ponies that I can remember that have the hoof heart variations are Cotton Candy, Minty, Butterscotch, Moondancer, Winter Snow, Wysteria, Tink-a-tink-a-too, Razzaroo, and Sweetberry.