Some breeders use colored bands for their litters to tell the puppies apart. Also a 4 week old puppy looks nothing like it will at 12 weeks. It's normal to have strange thoughts like this but its great to have a breeder that you are comfy with too. My breeder was great to work with. Below are pictures of my Jeter at different ages. His breeder was great with sending us pictures and also I lived close by so I was able to go see him a few times and hold him. I trusted my breeder though it did helped that he was smaller then his brother so it was hard to mix the 2 boy's up. He was close in size to one of his sisters but when you checked to see if you had the boy you wouldn't mix that up
In the first picture Jeter is 3 weeks old , next he is 5, then 9 then 12 and by the last picture he was 16 weeks.
http://i225.photobucket.com/albums/d...06/a_jeter.jpg http://i225.photobucket.com/albums/d...rame06/fgh.jpg http://i225.photobucket.com/albums/d...thJeter024.jpg http://i225.photobucket.com/albums/d...6/100_2334.jpg http://i225.photobucket.com/albums/d...ry32008149.jpg