Hi Stan & Joe:
It would probably be more accurate to refer to those items as Asian or Oriental restraints rather than Chinese. While there is no way to know for sure, my guess would be that they are probably Tibetian in origin for several reasons.
China lacks significant metal ore deposits and iron historically was and still is a prized item, nearly all of it having to be imported. Tibet, however, is rich in iron ore deposits and has a long history of metal working. As you can see, these restraints contain a lot of iron which indicates they are not of Chinese origin.
The geometric patterns on both items suggests a Buddhist influence (the predominant historical religion in Tibet) rather than the assymetrical, nongeometric designs associated with Taoism and Confucianism (predominant in China). Again, this is not determinative, just suggestive.
As Joe surmised, these are not "handcuffs" as we commonly understand the word today, namely a device to restrain a prisoner, but were more "ceremonial" in intended use: namely, to publicly humiliate someone who had committed some transgression against the community peace and dignity, much as Westerners used the stocks and pillory. While generalities are always suspect, and the range of cultures in Asia quite diverse, the Buddhist influence of non-violence found in Tibet would lend itself to such a punishment, rather than a caning or other form of corporal punishment more apt to be seen in China.
Typically, the offender would be fastened into these items and then paraded about as an object lesson for the community.
The seller of the second restraint indicated that the dimensions were 11 inches by 5.9 inches. Due to the diminutive nature of people in that area, it is quite possible that this device may have been used as a fetter to shackle two people together, left ankle to right ankle, much as the Europeans used a shrew's fiddle to harness two gossipy or scolding women together by the necks. While the apertures in the restraints would serve to securely manacle a modern day Westerner, they'd probably slip off the wrists of a typical pre-20th century Tibetian, Mongolian or Chinese individual.
In any event, they're nifty items and illustrate both the historic similarities and differences among different world cultures. I hope the buyers of each enjoy and appreciate them.
Franklin