The Brainiac example showcased above represents one of these department store catalog offerings. Interestingly, a marked down J.C. Penny sticker resides on the upper left corner of the blister card. I suspect overstock catalog merchandise like this piece may have been offered in actual stores at clearance pricing to move old product.
These carded & bagged Super Powers figures were supposedly offered in the Kenner employee store in this fashion as well. Although I've seen these blisterless cardbacks referred to as "proof cards" on occassion, I consider them strictly as unused cardbacks due to their direct retail links. Proof cards on the other hand served specific industry-only functions (creation of carded samples for example) and were never intended for release to consumers. Although unused cardbacks are virtually identical in many instances to proof cards, the intent and purpose differ substantially. As such, I believe the term "unused cardback" is best suited when describing the catalog mailer blister cards.
Green Lantern, Aquaman, Lex Luthor, Brainiac, Joker, and Desaad represent the characters I've been able to locate thus far in this format, but additional characters most likely reside in other collectors' hands.