Eric,
The symbolism of the superimposition of the Monarchic crown over an identifiable symbol of Scottish identity is rather obviously asserting the crown's "superiority" over Scotland. The fealty of Scotland's citizens, however, may lay elsewhere. ;) The same symbology is used in the cap badge of the Royal Irish Regiment, a crown superimposed over the Irish Harp. The crown and thistle is used mainly within the framework of military heraldry, and is sometimes used in civilian cases as well. Hope that helps a little.