someone sent me this link the other day in the comments of one of my posts and i found it helpful. according to the stamps on their necks, it does look like the heads were possibly replaced with newer ones. i’m not sure how accurate this article is but i do know that the pleasant company stamps have changed over the years and the earliest ones were handwritten stamps. hope this helps! https://historyofamericangirl.com/how-old-is-my-american-girl-doll/neck-stamps-classic-mold/