Tumbledown's Improbable Pallette registered on AKC color black and tan viewing pedigree probably was a red sable.
Raebark's Cinnamon Snap, Raebark's Spicy Nutmeg were sables Tumbledown'a Queen Of Spades registered with
AKC as Black and Silver possibly a sable no picture. Tumbledown's Recidivist could be masking red sable as sable is the top dominant gene.

Registered as Black/Tan on AKC 

Pallette is a black & red brindle.  When she was a very young puppy, I at first thought she was a black but with the weirdest leg shadings I ever saw. I soon realized that what I was seeing was brindle.  Brindle in the GSD is a dominant spontaneous mutation affecting the ground color (the tan/red/cream/silver) of the dog. Typical of a dominant spontaneous mutation, she was the only brindle in the litter.  When she was nearly a year old, circumstances put me into a situation where I couldn't actively breed GSDs so I let her breeder take her back so she could be utilized in a breeding program.  The photo with this pedigree was taken when she was nursing puppies and out of coat.  Somewhere I have a better show pose photo of her when she was about 11 months old.  When I find it, I will replace the current photo with that better one.  I believe that the mutation for brindle occurs regularly in the breed, but most brindles probably go unnoticed by the GSD world because for a brindle to come to the attention of the GSD world, it has to first fall into the hands of someone who recognizes it for what it is.  Although Pallette being a dark dog is an attractive brindle, the lighter brindles especially brindle agouti/sables aren't particularly attractive to most people and this may be why brindle in the breed isn't actively perpetuated.