My gulf coast/three toed integrade has that plastron as well.I'm going off Carapace and plastron markings and comparing it to the ornate/ 3 toed hybrid I have. My 3 toed/ornate juveniles I hatched last year have the same plastron markings as this one.
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These are the hybrid
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This is a full 3 toed.
Who knows though, we never can tell for sure about the markings because so many come out differently