if you look at the links that chessie posted...about spotted/tan marked purebred Labs...you'll start to see that there may have just been the one father and he had the supressed genes (on the Lab side of him) to possibly produce a tan marked pup (regardless of it being mix breed). i think, as long as they are sure there was just the one sire, that the supressed Lab color gene came out and could have something to do with the extra "spots" on the pups.