The Fortune coat of arms seems to come in 2 or 3 styles the most common one seems to be the one to the left. A stag upon a yellow wheel, surrounded by eight penzants.The motto is Fortuna fungacior undis, meaning Fortune is more transient than the waves.
This coat of arms was acquired by my great grandfather, John('Jack') Fortune of Bengairn, Castle Douglas, Stewarty of Kirkcudbright, when he purchased the Bengairn estate in Galloway around 1903. We have the correspondence between him and the Lord Lyon of Arms in Edinburgh as well as the original illuminated painting of the blazon. The wheel is a 'rebus' or visual pun, on the name 'Fortune' and the golden 'pezants' or discs are a reference to the origins of his prosperity in East India trade, as is the 'chapeau' or ermine-trimmed red cap which should be shown above the shield under the stag crest rather than the wholly spurious helm shown in your illustrations. It is a mark of my grandfather's having graduating from being the son of prosperous farmers in Fife to being a laird in the august ranks of the landed gentry rather than a mark of nobility. (just so-o-h nineteenth century!)
If one cares about these things the only people entitled to 'bear' this insignia are my brother and I as the two direct male descendants. So beware-"Nemo me impune lacessit"!
By the way there is little likelihood of our branch having Irish connections. We would seem to be 100% Caledonians from Fife with perhaps some connections to Lothian, Kincardine. and Angus.