Some ferrite beads are intentionally lossy, and are generally used for EMI suppression. I wouldn't think these would work as a pulse transformer, and I don't think they look significantly different from beads meant to be used as inductors and transformers. Ferrite beads come in a huge variety of permeabilities, effective frequency ranges, etc. Can you give us a part number, or at least a material type?
Otherwise, I guess a guy could just take an unidentified bead, wind a transformer, and see if it works.
EDIT: of course, I could be wrong. If so, I'm sure someone will let me know.