As was already noted, the loose cards are blow-in cards. The attached cards are bind-in cards.

Bind-in/Blow-in cards/envelopes

Subscription devices, usually standard size postcards, which are either inserted or bound into a magazine. The card/envelope should have a business reply mechanism and should allow individuals to charge-or be billed for-the subscription. Magazines that do not have the capacity to invoice should select envelopes which allow for the easy return of personal checks. Bind-ins/blow-ins are used predominantly to convert single-copy buyers into subscribers.


From http://www.clmp.org/resources/glossary.html#bind