There’s an explanation of this card at this-old-jeep.com.
“Quaker Oats Sparkies Jingle Contest postcard featuring Terry & The Pirates!!
Puffed Wheat and Rice Sparkies
1946 vintage animation cartoon art postcard
Milton Caniff artist
Terry & the Pirates riding in a Jeep
Reg. U.S. PAt Off. Copyright 1946 by News Syndicate Co Inc ~ Artist signature United States government issued postal stationery. Some stains as show below.”