This is a stupendously fancy bridle, modeled here in a the collection at the Royal Mews in England. The Royal Mews is the stables at Buckingham Palace:
"One of the finest working stables in existence, the Royal Mews at Buckingham Palace provides a unique opportunity for visitors to see the work of the Royal Household department that provides road transport for The Queen and members of the Royal Family by both horse-drawn carriage and motor car.
The Royal Mews has a permanent display of State vehicles. These include the magnificent Gold State Coach used for Coronations and those carriages used for Royal and State occasions, State Visits, weddings and the State Opening of Parliament. A State motor vehicle is also usually on display." (link)
This golden bridle is part of the harness for the Gold State Coach mentioned above,which can be seen in the background. Check out the photostream on flickr for more photos.
Photo: mharrsch on flickr.