... The quantity you sign up for you will receive in return. And since I signed up for the maximum(lately 50 to 60 cards), you would get one from me.
Not necessarily Chris. Also the participants who sign up for the max will get as many cards in return as they send out. The max just means that you do not have a limit. Maybe we should have called it unlimited in the first. Only if both of you sign up for the max it is certain that you will end up in each others group.
@Jan: As Chris already described, you can send whatever size your post office accepts as a postcard. I would not recommend using an envelope - it is a postcard exchange, not a letter exchange. That some cards arrive a little bit worn out is part of the exchange. For each round I also collect the card I sent and I send my card to myself just because this is more authentic

And sometimes I end up with my card being damaged on that short way. Also you are free of materials you print on, be it RC, fiber or some alternative processes. I received postcards which were photograms, polaroids and even small instax prints. There is only one rule, the origin has to be analog/traditional. Well and there is another rule: Once you signed up and the round has started you will have to fulfill your commitment.
Cheers
Ruediger