Rumball, typically if you hold the bird and look closely you can see little quills where the picked out tufts were. Although many times, they'll tear the whole skin piece off and completely remove the quills, so you may have a tough time telling. Legbands help to mark birds and keep track of this kind of stuff, so if they do look alike, you'll know who has which traits. I don't consider 2 yrs to be old for a chicken, in terms of laying, unless they are forced to lay over winter via lights and never allowed a break. I have araucana that are 6 years old and still lay regularly and have hatched their eggs. It's all a matter of how the flock is managed and overall health of them, imo.