As far as I know though the Dorking is the only one with the single comb. And if it was just throwing an odd sport I would only expect one or two every few generations. Through time I would expect it to go nearly totally dormant.
Now these hens were mated to a single comb NN rooster and out of the eight chicks we also got only two had the extra toes, one of those had the lack of comb but all of the others had single combs and four toes.
It really appears to me that these hens were out of a first mating and the trait was not yet set. But mated with what?
In the pic that is the extra toe and it is nowhere near the fourth toe but comes out on the side of the leg like a spur button, in fact most are just below the spur button.
Now these hens were mated to a single comb NN rooster and out of the eight chicks we also got only two had the extra toes, one of those had the lack of comb but all of the others had single combs and four toes.
It really appears to me that these hens were out of a first mating and the trait was not yet set. But mated with what?
In the pic that is the extra toe and it is nowhere near the fourth toe but comes out on the side of the leg like a spur button, in fact most are just below the spur button.