Hi, BH – Chas has given you some good advice, as has Cajunscot, but there is more to say on the matter.
I agree that it would be wrong to display anyone else’s coat of arms — in or outside your house, on your vehicle, your clothing or your skin.
It would be acceptable to show a clan crest in monocolour — in that format, it is an acknowledgement of the clan chief as your chief.
However there is a place for flipping an armorial device, and the right shoulder is an appropriate place for it.
In the South African Army, each unit has a coat of arms (shield only) which is impressed in plastic on a pair of shoulder tabs (tabs that hang down the sleeve, that is, not along the shoulder). In some instances, enamelled versions are worn.
Note I said a pair of shoulder tabs: if any charge in the device faces to the dexter side (the right-hand side as seen from behind the shield, so the left as seen from in front), it must face forward on the shoulders.
So where the charge faces the dexter, that shield is worn on the left shoulder. The shield with a charge facing the sinister (left as seen from behind) is placed on the right shoulder, so that the charge is still facing forward.
In many unit arms there is no left/right differentiation.
But nowadays many unit arms are also displayed on the shoulder with the national flag. Again there is a left and right to that. The flag flies from the hoist to the fly, and on the left shoulder the fly is on the left (or dexter) side. But on the badge made for the right shoulder, the fly is on the right side, because the fly is on the left (sinister).
So the soldier who puts his shoulder tabs must make sure that the black and yellow part of the flag (the fly of the South African flag) faces the front, and the point of the green pall faces the rear.
The same principle applies to any other device worn on the right shoulder, be it a flag, a shield of arms or a crest.
If you wear the US flag on the right shoulder, the stars are on the front side, and the stripes are on the rear.
If you wear it any other way, it is back to front.
The crest that BH wants to use would need to be redrawn, because it would be necessary for the correct hand (the right hand) to be shown, but with the cross facing forward (the viewer would need to see the back of the grieve, or metal “glove”).
When knights wore their arms on their surcoats, this principle applied there, too.
Where a lion faces to the dexter, he must face to the dexter on both front and back. So he faces the right shoulder on the front of the surcoat, and he still faces the right shoulder on the back – that is, he has been flipped around to face the correct way.
Regards,
Mike