For what it's worth, over times in the past I replaced the same missing screw from screws I salvage from old Remington typewriters. They were identical. later I discovered that S&W apparently made some typewriters, circa the same time period as this revolver, either as sub contractors or under their own name. I've seen one of these with S&Ws name on it and discussed it with Roy Jinks. His opinion was it could be a "one-off" or spurious, as at that time ( yrs ago) he could find no records at the factory to authenticate typewriter production. Ed