On "From Her Majesty's Jewel Vault" website, it is mentioned that the Court Cicular (which I could not personally find, unfortunately) mentioned that, on the same day of Her audience with First Minister Nicola Sturgeon, The Queen had an audience with members of the Argyll and Sutherland Highlanders Regiment - which would of course be a strong argument in favour of the badge of this regiment, rather than of Cullinan V Brooch!