9.5x12.25x2" deep box w/text reading "Hi Kids!/Do You Want To Be As Big And Strong As Hopalong?/If You Want To Sit Straight In The Saddle, Pard, And Have Muscles Like Hoppy's To Show...Just Use Hoppy's Muscle Builder Each Day And See How Your Muscles Will Grow!" Facsimile signature to right of Hoppy image reads "Good Luck From Hoppy." © Wm. Boyd. Note on one side panel reads "Dear Parents/This Exerciser Is Designed In A Sincere Effort To Help Build Strong, Healthy Youngsters. Your Cooperation Is Needed To Encourage The Daily Use Of The Exerciser According To The Instructions. You'll Be Proud Of The Results." Made by Dyer Products Co., Canton, Ohio. Box includes 1x20" long rubber belt w/horseshoe-style ends that are 2" wide. Embossed in rubber reads "Hopalong Cassidy Muscle Builder." Rubber is pliable. Paint is Exc. 1.75" dia. by 6" long rubber dumbbells w/embossed lettering on each end reading "Hoppy/Bar-XX." Two 7.5" long rubber pistols designed like regular revolvers but are formed out of molded rubber. Grips have embossed steer head and read "Bar XX." White painted grips. 2.5x7" "Muscle Building Course" that unfolds to 10x14". Detailed text and illustrations give seven easy lessons to be done once each morning and once each night. Two bw photos of Hoppy are on instructions. 2x6.5" double-sided instructions for use of "Hand Exerciser Guns/Dumbbells And Foot Exerciser." 2.75x5" business reply envelope addressed to "Hopalong Cassidy Co. Dyer Products Co. 514 Second Street Southwest Canton, Ohio." Box lid show lt. wear but no broken corners or major problems, box insert is concave due to weight of rubber equipment. Instructions show lt. aging. Box is Fine, instructions are VF, equipment is Exc. Only complete set we know of. 1950s. Rare.