yep, those are manacles for sure. Probably late 1800's at the earliest, judging by the locking mechanisms, but more than likely early 1900's to 1930's if I were to guess. Those are in pretty nice shape. Be careful cleaning or otherwise, as that would destroy the heritage of them.
Maybe someone in the family was a constable or deputy way back when.
Don't let them go, unless you do find a good home for them (museum). If you find they belonged to a family member, that makes them even more valuable!!!
Awesome find!!!