Stamp cards, or trade cards, are filled out according to card worth. If you trade two regular cards for one special card, or vice versa, both you and your trade partner would mark off two boxes. A trade / stamp card is considered completed after 25 boxes have been marked off. If you would like to donate a stamp card / trade card, please do so on the site forums. Stamp cards are not required. As long as you keep track of how many cards worth you have traded in your logs, then you can claim stamp rewards.