27" x 41" mylar poster.
In 2015, one of these sold for $3,750. The usual price for one is just $300-500.
Variant #1: Gold. This version was a limited edition of 500. However, theswca.com reports that half were destroyed due to printing error, making them even more rare.
"Jeff Kilian has reported that there were 250 gold and 250 standard release posters. Out of the 250 gold mylars, half of them were destroyed during the printing when the ink stuck to the faces of other posters. There are at the most 125 of the gold mylars in existence because of this." — originalvintagemovieposters.com
Variant #2: Silver.
Both also have sub-variants, where the first batch says "test proof" on the edge. These are very rare.