A George III silver mounted cowrie shell snuff box

A George III silver mounted cowrie shell snuff box,

maker's mark only, I.R in a rectangular punch, probably Scottish, circa 1790,

the mount with engraved borders, the flush hinged cover engraved with two crests, monograms and mottos, length 9cm.

The monogram, crest and motto are those of Yates of Scotland and or Morison of Prestongrange, Edinburgh.