I can't speak for cards, but it is not unusual for a postal authority to reprint stamps.
Sometimes this is because more are needed for postal use that was anticipated.
Sometimes an older stamp is reissued or reprinted from the original plates for collectors. (This is very uncommon today, but happened a lot in the 19th century and early 20th century.)
And sometimes they are counterfeited.
But.
The reprints will have differences.
The paper is different. (laid paper thick paper india paper-- it's endless) A reprinted card may be on a lighter weight card or a greenish rather than a cream coloured one.
The ink colours are different (red, red-orange, claret, dark red )
Engraved stamps may have re-entries where the plates were re-engraved after wear. On a card, this could mean the reprint was made by photographing a particular card rather than using the original plates or photos.
Different printing types (engraved, photolithography)
Different sizes. Even from the same manufacturer, the reprint may be cut larger or smaller, although the difference may be less than a millimetre.
Perforations-- this is peculiar to stamps but the teeth on a stamp may vary.
Philatelists will tell you all about it. Excellent cure for insomnia, actually.
There is a perfectly respectable sub-gentre of philately called "Fakes, Forgeries and Cinderellas". Sometimes the phoney stamp is worth more than the original!
