How about starting some sort of contest to test your knowledge of the collectible camera? No real prize, no, I don't have any Leicas to give away, just the pride of answering correctly. And now the question(s): The Leica M3 series come in two versions, Double Stroke and Single Stroke (winding levers). The Double Stroke was manufactured first with the Single Stroke taking its place later. What was the reason behind Leica creating a Double Stroke winding camera and why was it replaced later with a Single Stroke?