My Grandmother owned a sweet dog, Poco and he was labeled a Sheltie. Well all the Shelties I've seen are small. While Poco had the personality and looks of a Sheltie, his height was probably that of a Collie. He was tall!! He was even dubbed the "Lassie dog" by some kids.
He was up to my knees and I'm 5'6ft. I have pictures of him, but would have to show you via e-mail because I'm not so good with this photobucket stuff. So is it possible that a dog could be a Collie/Sheltie mix?