Modesty prohibits me from naming the buyer, except to say my wife has now, almost, forgiven me for the cost !
Marks are only the Lion Passant of London 1740-1756 and the maker's, which is unrecorded as far as I can tell. The rebus is, I think, a cup and cover. The Golden Cup was a quite common shop sign and address for goldsmiths in this period , but not recorded to any I A one as far as I know . However two intrepid heroes of 925 are currently searching for the Golden Cup !
My own thought is perhaps John Andrews of Brick Lane. Probably wishful thinking.
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Stock buckles are not uncommon, they fastened at the back of the neck to secure a fancy cravat called a stock. Found from around 1730 until mid Victorian time and are a conventional buckle, albeit with three, four and, occasionally five studs on one side only
Stock clasps are rare survivors, I've only ever seen three or four in English silver . They were worn, I believe, at the front of the throat, often by the military . They seem to have gone out of use by 1750 - 1760

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Size is 44mm by 52 mm.