This is actually a karuta set, although it doesn't have your typical hiragana/katakana letter on the front. There are corresponding reader cards, but not in the auction I picked up. This set likely came in a magazine from 1956 as there are perforations and cut lines on the cards indicating the intent for a kid to cut them out of the magazine. There are 29 cards in the set including these 6 sumo wrestlers, 14 baseball players, 4 pro wrestlers, 2 boxers, 1 swimmer, 1 marathon runner, and 1 judo fighter. All of them are equally amazing in terms of image quality. They measure approximately 2.0" x 2.5", but I am not sure of the real intended dimensions as the set I picked up is somewhat hacked....but I love it since it shows that some kid back in the day actually held these and cherished them as well.
Kind of reminds you of the 1953 Topps Baseball set, right?