19th/20th Century: http://www.rockislandauction.com/viewitem/aid/68/lid/3151
16th Century: http://www.rockislandauction.com/viewitem/aid/68/lid/3170
When someone makes a "fake" historical gun, they can do so with the intent to deceive or be up-front with the gun's new manufacture. Those acknowledged reproductions are a great option to have - guns like Uberti reproduction revolvers give us an excellent opportunity to shoot antique designs without the cost of true originals and without the risk of damaging them. On the other hand, creating "antiques" fraudulently to deceive someone into believing they are actually originals is a reprehensible practice.
What about when you don't know, though? In the Victorian era, it was popular to have fancy antique guns - like these wheellock pistols. Just like today, not everyone could afford to actually go buy a 300-year-old ornate gun, though. So, many people would commission new replicas made (and I'm sure plenty of fraudulent copies were created as well). Fast forward a hundred years or more to the present day, and we have a bit of a conundrum for the potential buyer. It a gun 100 years old or 400? It takes some substantial experience and knowledge to be able to tell the difference - and yet an acknowledged Victorian copy is still a potentially fantastic piece of workmanship and collectible in its own right.