Duncan Mr. Yo-Yo circular patch not made by Duncan, but made by Mann Manufacturing, Inc., of El Paso, Texas 79994 (1946-1977). Mann was a maker of young men's apparel, among other things. The patch originally came stapled to a yellow card with Duncan's Mr. Yo-Yo man pictured on the card. The patch was stapled directly over the image. Below the image were the words "Official Yo-Yo Jeans". While I was unable to find any information on how these were retailed or distributed, the mounting card suggests that the patch/card was attached to pant jeans and retailed among young boys (and possibly girls) apparel at stores such as JCPenney and Sears, from about 1970 to 1977. Mann went through dissolution sometime in 1977.
The lower portion of the cartoon character's shirt says Duncan. The patch is slightly larger in diameter compared to a Boy Scout merit badge. The backing of the patch is similar to the backing of a merit badge you would see today.