The easiest 'fix' would be to remove the outer ring and fit waterhouse stops or washer stops. 'Paul I know this thread is a little old but I just picked up a 420 dogmar myself and mine is also missing the aperture mechanism, small world, anyway I was wondering if you ever found replacement parts or created something that would work, thanks.' Actually I have 3, the other 2 work well. Goerz American Optical Co., 1906 Army & Navy Binoculars (pre 1913). Goerz American Army & Navy catalog, just after move to 317-323 E.
