I read your post.  I think there might be a misunderstanding about Marshall
tatooing.  Four of our five ferrets are from Marshall Farms.  We have the
health guarantees from Marshall Farms to verify it.  They have two blue (or
purple) tatoos on their right ears.  This is how Marshall's tatoos their
ferrets.  This is from Dr.  Judith Bell, one of Marshall's veterinarians.
If you have seen ferrets in your area with a single black dot, more than
likely they are from a breeder other than Marshalls.  Sorry to burst your
bubble.
 
Peoria Area Ferret Connection
Mary Oyer
[Posted in FML issue 1472]