This is a strap that came with an American vintage saxophone when purchased, likely from the late 1950s. Please check the photos for the condition. The length of the chain part can be adjusted by pinching and moving the metal fittings, and it operates smoothly. It appears to be similar in specifications to the strap used by Art Pepper in photo 6. In terms of size, it's just right for an alto saxophone, but I think it might be a little short for a tenor.