Looking for information on very rare coat color.

Hello, I am looking for information on a particular kind of dog that I was told was a German Shepherd, but had a grey/brown sable coat with White mask, chest, legs, paws, and underside. The type of coloring a Siberian or Malamute would have.

The appearance was Shepherd-like, with the tall standing ears, body weight and conformation, skull structure, etc. except for the unusual markings. I've heard rumors that these dogs were being bred in Canada around 1950-1985 or so.

Breed clubs can give me no information. Anyone who remembers the old Canadian show "The Littlest Hobo" will know the type of dog I mean. I've also heard rumors that that color can be produced by crossing a sable GSD with a white GSD. Does anyone know if this is true or has any other information?