Probably a boy. (The hair is parted on the side, which was more common on boys.) Mat is stamped “Holmes
You can barely see a woman holding the baby still on her lap. The original has touches of metallic gold at the child’s shoulders & on the little finger of its right hand.
Cartes de visite
(Yes, she’s sucking her thumb.) Photographed by Wenderoth, Taylor & Brown, 912-914 Chestnut Street, Philadelphia, Pennsylvania
Note what appears to be a fancy paisley shawl draped over the chair & embroidery on the child’s jacket.