Cleaning a Stiff Aperture Ring on a Leica Summitar Lens

Some years ago, I acquired—in perfect working order—a dumpster Leica IIIc and Summitar lens. It was dumb luck then as it is now and I love a user-camera. Little did I know that I would find myself enamored by the Summitar. My version is a 10-blade, single coated version post World War II, in the 621000 serial number range. Frankly none of that metadata matters; with old gear as in new, I just load…