Artist's Proof
Print intended as a point of reference,
for production of an edition. They are believed by some (incorrectly
usually) to be the perfect print because the artist uses it as
a template for how print should be.
Either way, it is common practice
to reserve approximately 10% of an edition for this purpose,
though that figure varies bettween artists. The french term "eprueve
d'artist', or simply "E.A." or "A.P." is
often left in the lower left corner of the work.
A word of advice. Don't get ripped
off and pay extra for an artist's proof. It's a sales gimmick
typically used by disreputable art dealers.