@ CT - Well, the Grant gives the crest thus -

and on a Wreath of the Liveries is set for Crest an eagle displayed Gules crowned of a ducal coronet Or, and in an Escrol over the same this Motto “AIR MUIR ’S TIR” and in another Escrol below the same this Motto “DIA ’S NAOMH AINDREA”;

Notice that both the crest and the motto are substantially different.

@ Kyle - frankly, I don't know. It is easier to say what it is not rather than what it is.
I get this feeling that it might be one of the newer clans that has been armigerous, but has now found a chief.

Regards

Chas