Complex sentence: He was credited with inventing and selling the first exercise equipment for the masses (machined dumbbells, spring pulleys and tension bands) and even his image was sold by the thousands in "cabinet cards" and other prints.
Split into simpler sentences: He was credited with inventing and selling the first exercise equipment for the masses: machined dumbbells, spring pulleys and tension bands. Even his image was sold by the thousands in "cabinet cards" and other prints.