Coat of Arms

[Mike_Oettle]

Boats, when you refer to a family crest, I hope you mean that you are creating an image of the crest of the chief of Clan MacThomas, inside a strap and buckle, which is the accepted badge of a clansman.
This is illustrated on the MacThomas website and shows a cat holding a snake (the actual crest) and, on the strap and buckle, the motto Deo juvante invidiam superabo.
Any clansman may display this badge in his home, or wear a metal reproduction of it on his bonnet.

The crest is the part of the heraldic achievement that sits on top of the helmet.
Together with the helmet, mantling (decorative flourishes), shield and motto it forms the full achievement, also called a coat of arms.
You probably saw the picture of the chief’s banner on the website as well. This shows the contents of his shield of arms in the form of a flag, technically called a banner of arms.
You may display an image the chief’s full achievement, or of his banner in your home, provided the display makes it clear that it is not your coat of arms, but that of the chief of your clan.

You have been advised to apply to the Lord Lyon for matriculation of the arms to yourself. This is one possibility, and (provided money is no object) the best possible way of doing it.
You will be granted a shield that shows at least part of the quarterings on the chief’s shield or banner, with suitable differences to indicate that you belong to a branch of the clan.
You might be granted the same crest, but more likely it will be a similar one or, if you so choose, an entirely different one. The motto you use can be one of your own choosing, but traditionally clansmen’s mottoes “respond” to the chief’s motto.
Such a matriculation will be quite pricy (the Lyon Court website will indicate the cost), but it will provide you with a beautifully illustrated painting of the arms, together with calligraphy that explains who you are and why you are being registered with the arms, as well as the blazon, or technical description, of the arms.

If this is beyond your means, you (as a US citizen) are by no means obliged to take the Lyon Court route.
When you have done the appropriate research, you can apply to one of the private registries in the United States. Another possibility is applying to the Bureau of Heraldry in Pretoria.
Neither a private registry nor the Bureau will provide a coat of arms that will necessarily be accepted by the Lord Lyon, but the Bureau will do its best to provide you one that is differenced in accordance with Scottish tradition, using the Stodart system of differencing (widely, but not too strictly, applied by Lyon Court).

My coat of arms is registered in Pretoria. It is an adaptation of a device my family has used for centuries, but in fact belongs to a family from another part of Germany which spells its surname slightly differently.
Now that I have registered my arms, any other member of my family may apply to the Bureau to register a similar device.
This would be an option open to other members of your family too.
Regards,
Mike