Georgian Gold & Agate Seal with Crest Intaglio of the Maclean Family

An unusual and quite large Georgian seal with The MacLeans of Coll Coat of Arms. It is a palish green agate and is mounted in 9ct gold and was made circa 1820.
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Below are the details of the crest.

The coat of arms of Alexander Maclean of Coll, matriculated in Lyon Court 24 February 1803: “Quarterly, first or, a hill rising from the base; second, argent, a dexter hand and arm issuant from the sinister in fess gules and holding a cross crosslet fitched in pale azure; third, argent, a galley, her oars erect in saltyr sails furled sable and flags displayed gules; fourth, per fess or and azure, in chief two hawk’s heads couped and affrontee gules, in base a salmon naiant proper. Above the shield is placed a helmet befitting his degree with a mantling gules, the doubling argent. In a wreath of his liveries is set for crest a battle-axe erect in pale, crossed by a branch of laurel and cypress in saltyr all proper. In an escroll above this motto ‘Altera Merces.’ Supporters, on the dexter a greyhound proper collared and leashed gules, on the sinister an ostrich proper, in its beak a horse shoe azure. Motto below ‘Virtus Durissima Terit.’ meaning “The hardest power or virtue” Motto above ‘Altera Merces’ meaning “Other reward”.