On eBay, user scatjazz04 sells a Becker hand [sale page link], advertising it as "rare antique late 19th century prosthetic articulated hand", further down advertising it as "very rare", demanding 1800 USD.
After this was posted, in the meantime, the item's description was changed to "early 20th century". Also that is not true, and it is definitely not rare or even very rare.
This is a Becker Lock grip hand, patented in the fourties of the 20th century (so not "early") and built to this day by the Becker family (hence the name). Its new price is 350 to 650 USD, used Becker hands never are worth more than a new one as they are not considered "antique" by any means. Why anyone would treat these as "late 19th century" items and ask horrendous prices is not clear.
Here are some images.
This artifact published on eBay [link] is advertised as an extremely rare authentic ancient Roman bronze prosthetic hand dated 0-400 AD. It is described to contain a fabulous multipurpose style with three fingers (each "very different" from the other), a twisted engraved design and beautiful dark green patina. It is described to be "in excellent condition". Apparently it is just 40mm in length and it is alleged to have been found in Europe. As the text says further, ancient soldiers would bury their valuable treasures before a big battle hoping to return later. The items they didn't bury were often lost on the battlefield. Unfortunately many soldiers were slaughtered, but they left behind many treasures for modern man to find.
Looking at the items, I wondered whether they could have been some kitchen utensil (stirring a soup with that could have been effective) or an instrument for gutting an animal (at that time, one would personally go hunt rather than buy meat from another person), of simply something different altogether.