I was out of town so I'm late getting back to this thread. WOW, jarnick, you have blown my mind on these cards! And given me some things to think about. Clearly, many of these cards were issued with the intent that the actual stamps be attached and cancelled. So in some ways they are much like Maximum cards. But they were nearly all issued to commemorate various philatelic events, so that would seem to qualify them as souvenir cards. It's a little amusing that some have cancellations over the stamp designs, although they are not valid stamps. Can you tell me whether there is anything on the reverse of any of the cards?
BTW, there is one -- Philex '83 -- which was previously given a catalog number since it was printed by a known security printer, Canadian Bank Note Co. It was issued with and without serial numbers (SO-30 and SO-31).