Sounds like a normal black and tan. Some lines (show lines) the normal black and tan will have what is called a "bitch stripe" which is sable hairs down the spine in a stripe.
Ironically, my sables (not sure this is true of all sables) have had a solid black stripe down the spine as puppies that persisted through adulthood.
NAPWDA Certified Cadaver Dog
Waiting at the Bridge (italics
=GSDs) (hemangiosarcoma=blue):Grim , Cyra, Toby
, Rainbow, Linus, Oscar
, Arlo & Waggles