Other than test mating, I'm afraid there is no other way to tell what she is "hiding" underneath that splash color that I know of. The splash color conceals the actual color of the bird, so there is no way to know if she is "over-colored", or will throw over-colored (mossy or with copper leakage) offspring. Her tail is nice and low for now, so her offspring should have decent tail angle. Her earlobes will be nice and red as she nears point of lay. Her eye color looks good best I can tell. Her legs look like they are a light slate. The fact that she is a big pullet is good, and will put good mass on her offspring. I would breed them and grow out the chicks to see what you get.
I had 3 splash copper hens I got as hatching eggs locally from a friend. I didn't know much about them other than they were supposed to be from the Bev Davis line. They didn't have great egg color and only laid a 3 at best on the Marans egg color scale. They were bred splash to splash for too long causing the egg color to suffer I think. But I got some eggs cheap and wanted to experiment with them. I culled the splash copper cockerels, and only kept the splash pullets and bred the pullets to a BCM cockerel. Their blue copper pullet offspring I kept look good and lay a little darker than their mothers. I'm hoping for even better egg color with the next generation, breeding the blue coppers back to their black copper half brother to reinforce dark egg color genes.
Here is one of the blue copper pullets, she is the daughter of the darkest splash copper hen I had. I think that had I not paired her mother to a very well colored male, she wouldn't have thrown offspring with color in their hackles. Her mother was more melanized than the other splash hens.
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Her mother was the darkest splash in the front. Sorry it isn't a great pic but it is the only one I can find on my computer.
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