Should we donate the value of the gold piece at the time it was found, or at its current price?

Whoever finds gold or valuable money is obligated to announce it for a full Hijri year (i.e., inquire about its owner). If its owner does not appear, then he is permitted to utilize it while guaranteeing it to its owner should he come. However, if the finder does not announce the found item for a year at the time of finding it, then it does not enter into his ownership. Instead, it should be given as charity with the intention on behalf of its owner. If the gold piece is not available, its current value should be given as charity with the intention on behalf of its owner.