Leitz Film Sprocket Guage
Comes with Standard Guage so you can check the sprocket guage for accuracy. Fits into the picture frame of camera, guage 'arm' is connected to sprocket gear tooth, guage needle registers on the scale letting you know if the sprocket gear needs adjusting in order to space film so there's no sprocket holes between each photo. M camera in photos registers good as you can see on the scale. This can be used on all M Film Cameras. Body shell needs to be removed in order to check. 2nd & 3rd photos show the guage on the Standard Guage for checking the Sprocket Guage.