Is it illegal to open carry Hinged Handcuffs?
In the absence of a jurisdiction tag...
england-and-walesengland-and-wales
No, but there use may constitute an assault or false imprisonment if one cannot justify their application was reasonable, proportionate and necessary in the circumstances.
A civilian can lawfully use reasonable force if the conditions of s.3 of the Criminal Law Act 1977 are met:
(1) A person may use such force as is reasonable in the circumstances in the prevention of crime, or in effecting or assisting in the lawful arrest of offenders or suspected offenders or of persons unlawfully at large.