i have some dominiques. the chicks look a lot like barred rocks. only difference i can see (and having looked up on the internet) is that barred rocks are single comb and dominiques are rose comb.
PLEASE NO ONE TAKE OFFENSE I AM ONLY OFFERING MY OPINION.....I COULD BE WRONG
This chick looks similar to my Barred Rock chicks but is alot smaller. After I realized how small it is I went to Feathersite and looked for a similar chick. When I found the breed below I knew instantly that this is maybe what you have. A Japanese Bantam either Black Moltted, Black or Grey color variety . I think so because of his short legs and low stature. I have below pictures of Barred Rock and The BTB Japenese. I think the chick is a Japanese Bantam. I could be wrong as it is so hard to tell at this age. Do you know which hatchery it came from or it's age? That would be helpful in finding out the breed. He looks so small in your hand and appears to be built right on the ground. The Japanese are known for their short legs and high tails.