A hard to find string pack sold by D.F. Duncan Sales & Promotions, Ltd.. Their yo-yo product line included the Pro-Spin Stinger, Pro-Spin Slinger, and the Pro-Spin Olympian. D.F. Duncan Sales & Promotions, Ltd. was the forerunner to Playmaxx.
String pack is from around 1984. Three strings for forty-nine cents. The 100% cotton strings were made in Mexico.
