The following is from 2 private responses I made. Thought maybe
I should post it to the list:-)
  Call the large animal hospital of a veterinary school and ask to
talk to their farrier. I think I've seen round horseshoes when New
Bolton Center (University of Pennsylvania) had open house a while
ago. They have a farrier shop and staff blacksmith(s). Their
farrier's job is orthopedic horseshoes and he's probably studied
horseshoes intensively. This is the main page of the site but the
phone number is for the school itself and/or small animal hospital
in Philadelphia (215 area code, doesn't get you New Bolton
Center).
http://flipper.vet.upenn.edu/NewBoltonCenter/
This gives the New Bolton Center phone number 610-444-4800
http://www.vet.upenn.edu/HospitalsAndServices/Widener/Appointments.cfm
  I do think some people use round ones for quoits, some people
use regular U shape for the game. They probably kept a pile of
old, discarded, horseshoes sitting on a shelf in the barn to use
for the game.
  I'm probably wrong (check with the farrier) but I think there
are times round ones may be used on horses and somewhere back in
the cobwebs of the brain I think oxen
use round ones but I'm not sure of either idea.
  I was looking for a URL for an artist blacksmith association for
myself and ran into this site for the American Farriers
Association.
http://www.amfarriers.com/
They might be able to tell you about round horseshoes.
  Extraneous information: Farriers are blacksmiths but not all
blacksmiths are farriers. My father worked for Samuel Yellin, who
did wonderful ironwork - gates, grills, lamps, tables, etc. (one
example - the ironwork, National Cathedral, Washington, DC) Most
artist blacksmiths probably don't know the first thing about
shoeing horses, although there are a couple of farriers who are
members of PABA (Pa. Artists Blacksmiths Association). The
colonial blacksmith was the most important craftsman. He made the
tools that the other craftsmen used, along with many of the
household items from hinges to cooking pots.
Marge Green