From the site of the American Society for the Prevention of Cruelty to Animals the title "Dip ACVB" is used. As the information I was reading was about certification or qualification, I assumed the "Dip" stood for "Diploma", however the following quote shows that it stands for "Diplomat":
To become a Diplomat of the American College of Veterinary Behaviorists (Dip ACVB), veterinarians must complete a residency in behavior and pass a qualifying examination.
I wasn't expecting that. My next thought was that "diplomat" can mean something like "a person holding a diploma", then in that sense the person with the title "Diplomat of the American College of Veterinary Behaviorists" makes sense because a person can hold a diploma from that college. But I've checked every free dictionary online, and only two related definitions are shown usually. The first one being roughly "a person representing a country". The second one, if given, is usually along the lines of:
- a tactful person skilled in managing delicate situations.
Random House Kernerman Webster's College Dictionary
I doubt that the "diplomat" in the abovementioned title means the definition I've just quoted, or any of the others I've found. In any case I could possibly find out what the college means by asking elsewhere.
But my question relevant to this site is can or does "diplomat" mean a person holding a diploma, or was it used in this way in the past? The dictionaries I've checked don't give any such definition.
Edit: As Lawrence has pointed out, dictionaries DO define "diplomate" as a "person holding a diploma".
In that case it may be just a spelling error. Note, I think this word is mainly used in the US, though Google NGrams shows double the frequency of it in AmE when compared to BrE.