Perhaps one of the most famous ancient coin forgers of the last couple of hundred years is Karl Becker who is known to have produced coin dies for well over 300 coin types. Whilst many were for the Roman series, in particular the gold aurei, he also produced dies for Greek and mediaeval European coins.
In his day, before the accurate reproduction of coins by photography, many of his coins succeded in deceiving collectors and curators of collections. However, in modern times with the accurate photographs of legitimate coins being able to be compared with Becker's actual dies, many of which are kept in the Berlin cabinet, he does not really confuse the experienced numismatist.
His career seems to have taken a number of paths, for example, by 1795 he was established as a wine merchant and from 1798 to 1802/3 he was in business in Mannheim as a draper.
There is a tale reproduced in Hill's biography of Becker that early in the 19th century he was sold a false gold coin of Commodus. When he discovered that it was false he tried to return the coin only to be told that it served him right for meddling in things he didn't understand. This may have been the catalyst for Becker to learn the art of die cutting so that he may take revenge on the fraudster which he eventually did.