Sir William,
I believe your comment that it is not a coat of arms is based upon the norms of English heraldic tradition as upheld by the College of Arms; the image of the familiewapen that Wynand provided is (I believe) registered under South African Heraldic Law.
Very roughly-speaking South African laws of heraldry (within my admittedly limited understanding) consider any symbolic representation, displayed in colours, on a shield, to be a coat of arms. If it is not displayed on a shield then it is a badge or other emblem.
I am sure Wynand could speak more fully, but the picture he posted appears to be registered in the name of an organization - the van der Walt Bond - and may be used by anyone in the world of the surname van der Walt (for non-commercial purposes).
For an English title I might call it the "Coat of Arms of the van der Walt Family Association"; it is de facto a Family Coat of Arms even though it might not be de jure.