but wouldn't they be relatively easy to fake for purposes of postal forgery?
Since they are engraved they would still be harder or near
impossible for these modern forgers to reproduce.
They usually fake the most common definitives
such as the Machins and here in Canada P(ermanent) stamps
which can be used indefinitely and makes it very financially
attractive for these crooks.
Some are so good that even a collector would have
difficulty in telling the fake from the genuine.
So how would the general public or a postal clerk or
a letter carrier know the difference, or care ?
Forgeries to defraud the post office are nowadays nearly
always printed via offset/litho by these gangs who produce
tens of thousands of these fakes.
But I'm sure it would be quite easy for someone
to run off a few thousand on a plain inkjet or laser printer