I have serious doubts on these being antique handcuffs given the time period these claim to come from:
Old chinese police handcuff ,The handcuff year about 1850-1900.With insurance is rare. The key is lost. Age: 1850-1899 - eBay
These were clearly copies of a western-style handcuff that made it to china. I do not think that handcuffs from the late 1800's looked like this. Not only that, but they seems to be doubling locking handcuffs. That would be extremely rare from that time, if ever available on any handcuffs at the time.
They are listed with a 'buy it now' price of $135 (Plus $15 shipping). That is probably the last givaway that these are not as old as claimed as if they were that old they would probably be selling for more. Instead, this pair languished on eBay, unsold.