Rick - I checked the latin motto book this morning to find the other ref. - there is no mention of this one, even under different combinations. I don't think that it is meant to rep. a 3rd son - they didn't think like this. Most probably the sword would be given as a gift when he was first commissioned - the two sets of arms , possibly, being from each side of the family. The centre part of a coat of arms are generally all that is used - they are known as Armorials and they sit on a cushion, called a chaplet. The shading represents the diff. colours that were in the silk. The chaplet used to be worn under a helmet to protect the head from metal rubbing. I appreciate that this doesn't give you a provenance - they will charge you , but maybe the Royal College of Arms in Lodon could help ?