Actually it is a serpent. It’s missing the mouthpiece and he just put the bocal or “leadpipe” up to his lips. A dulcien’s key(s) are arranged differently and the bocal is a much smaller diameter. There are 3 types of serpents, church (squiggly w/no keys), military (squiggly with keys), and Russian serpents like the one pictured. Dulciens often have one key operated by the thumb at the base of the instrument. Not a dulcien.