This is a very interesting restraint which closes somewhat like the Muehlenfeld design, but secures with a padlock through two metal tangs, one of which is triangular. It sold for $350.89 after 13 bids.   This was listed only as "antique handcuffs iron shackle w/ lock at top Victorian era" and the seller states there are no visible stamps or markings. I do not know much about this type of restraint but it certainly appears legitimate, based both on the quality of construction, the deep textures and patina, and the amount of interest and price paid.