I'm trying to visualize what you describe - it doesn't sound like a
silver mitt.  How dark a brown?  Milk Chocolate? coffe and cream?  Dark
as Coca Cola?  A silver mitt is normally black with white markings.
Does your ferret have white spots on the belly or kneecaps on the hind legs?
Ark the legs noticibly darker than the back?  The belly marks would
indicate the traits of a panda or blaze.  If the legs are darker that is
indicative of a siamese or point mitt.
 
bill and diane killian
zen and the art of ferrets
[Posted in FML issue 1211]