A dexter arm in armour embowed and grasping a sword is a surprisingly common crest (I believe it is associated with the Wallaces, MacDonald of Clanranald, and the Dewars, among others). If I remember correctly, it wasn't all that uncommon for armigers, especially those of higher station, to wear their crest in a strap and buckle rather than the circlet.

For these reasons, I think you may have a hard time finding the bearer of this crest - especially if he was an individual armiger and not the head of a clan or family.

That's not to say you should stop looking, though!