I have no idea whether it's a period artifact or a recent artifact, but here are a few interesting tidbits:
1- Honi soit qui mal y pense- this is the motto of the Order Of The Garter. It means "Shame to who thinks ill of it (the Order).
2- Dieu Et Mon Droit- translates to "God And My Right", it is the motto of the King or Queen of England. It refers to the authority of God and the Divine Right of Kings to judge and rule.
3- 1759 is the "Anno Mirabilis", the "Marvelous Year" when the British had a series of victories over the French during the Seven Years War (the French and Indian War were just the incidents of that war that occurred in North America). It was bandied about much like we hoorahed 1776.
4- The lion and unicorn are heraldic animals of the King's coat of arms. FWIW, it was punishable under the law for anyone other than the King or an officer of the Crown to display the King's coat of arms.
5- Another FWIW- re-enactment is not a new thing, and there have been re-enactors for 200 + years acting out famous incidents of the Revolutionary War era. This means 200+ years of fake uniforms, fake artifacts, fake documents, fake militaria in general. A friend of mine's grandfather used to use a supposedly authentic Brown Bess for re-enactments before WW2.