Antique Pin from the Pawn Shop

I was at the local pawn shop when I saw this little beauty. Finding any jewelry with it's original case is rare enough, having the makers name is wonderful provenance. I love the simplicity of a single brilliant diamond. The pin is for a cravat or kerchief, I think. I can't see any makers marks on it, but I might need better optics. The case is some type of leather, with a dome formed front, lined with blue velvet & cream silk with the name Wm. MAGGS, JEWELLER, FOREST GATE AND ILFORD. The pin has three twists, the gold is reddish in hue, the diamond is approximately 1/3 karat, (I need a better picture) is spectacular & takes my breath away every time I open the case to admire it. I haven't been able to find out much about the maker other than there was a person of that name & address (in England) who was a watch maker in the 1800's. Whether or no he made jewelry or made this piece I don't know yet.