I wouldn't be surprised if your ground checked bird didn't have one. I bet coots are like Canadas, there are like 20 different subspecies and without putting a finger up their butt you can't tell which is which. I mean a red dot is an easy marker but do they all have them? I've seen several different bill shapes at least just googling "coot" you know those aren't all the same.
you have gotten way to hands on with your decoy carving