Thank you for this. I have two horse-brasses that each show three horse-shoes with seven holes, 4-3. Now I know they're right-horse-shoes, assuming they're pictured from above! I note that the county flag of Rutland (United Kingdom) shows a left-horse-shoe (if viewed from above).
If anybody can supply a more conventionally authoritative source than 'a post I saw on the internet', I would appreciate it!