Kenner's packaging vendor LPK produced Star Wars designs and artwork that were trialled on press proof cards 1977 during the lead up to the release of action figure blister cards in Q2 of 1978.
This Chewbacca from that early test run features an above production quality print on heavy card stock, square bottom corners, a printed back with 'Tusken Raider' text rather than Sand People, in addition to having a noticeably different to production, offset punch.
Proof cards such as this were never made available to the public, and were used internally for marketing, photography and sales related purposes (in addition to proofing the blister card design and sometimes even text, as evidenced by the Tusken Raider name change).
This vintage 19777 Chewbacca graded a stunning AFA 90, which is rare for most surviving vintage Star Wars proof cards, and there are none higher.