The commemorative stamp was issued 50 years after the Marshall plan George Marshall was honored because he had

proposed economic aid from the United States to rebuild the economies of European nations

Explanation:

Unlike other regular postage stamps, commemorative stamps are issued to honour some event, activity, or person of national importance. On the other hand, regular postage stamps go out of circulation after their supply is used up.

The commemorative stamp was issued 50 years after the Marshall plan George Marshall was honored because he had proposed economic aid from the United States to rebuild the economies of European nations.