I am afraid that that is not the case.
The very fact that a system of
mint mark and issue controls was introduced by the
Romans and maintained for so long is widely seen as a response to internal
fraud. We don't know how much of it went on but the fact such controls lasted for centuries indicates they were required.
We also have the so-called Felicissimus rebellion under
Aurelian. This revolt, which lead to a huge number of deaths, supposedly resulted as a response to Aurelian's reforms aimed at preventing
fraud and theft at the
Rome mint. Though counterfeiting coins was not mentioned in the sources, only stealing silver, it is very hard to believe that no counterfeining took place.
The systems in place certainly deterred the lower ranks from engaging in counterfeiting on their own initiative but when the higher ranks (Felicissimus was a rationalis who was in charge of the
mint and silver reserves of
Rome and more) were crooked then anything was possible.
Shawn