I always did like the later style as it had built in secondary mounting holes molded into them. Mine of course is this one. See picture.
Frank, I think you are on the right track but then if it were a Timex, instead of Cox, it could take a licking and keep on ticking! But then again I am not John Cameron Swayze, noted and respected newsman.
Jim, I think I remember the after market mount you refer to. Wasn't it molded of white nylon (or some such) and was packed with a piece of fuel line and a small balloon to be used as a fuel tank? Might have even had the mounting screws on the original packaging.
Robert