Oh wow i nearly fell off my chair when i saw the photo....i know that my mother has an identical pin in her collection......and can remember her wearing it in the late 50s as a kilt pin.......will have to dig it out and take a photo of it........have to go and buy a lotto ticket....never seen another one like it till i opened your post:)
It looks like it's marked R.A. That would be for Robert Allison, a silversmith who worked with and took his inspiration from Alexander Ritchie, of Iona, Scotland.