Over a year ago my wife found a gift card next the entrance to our building. She put up a sign (then) and no one called.
Can she use the gift card (we found out there is 200 shekels left on it..)
If it was a gift card of 200 shekels, and there are many such cards sold, then it may be use without a problem. This is since there is no more chance that someone will come to claim the card, it may be used. However if it is a card that was partially used, then it isn’t clear if the card is considered to have a siman on it, (the amount of money left in the card) or not. (An item that has a siman on it may not be used when found) What may be however is that before using the card, you should write on a piece of paper ( and keep the paper somewhere) that states that a card was found with X amount of money left in it. This way even if it would have a siiman, it may be used.