True, it has been tweaked over the last half century, and today's Leica MP and M7 have slightly improved range/viewfinders and built-in meters. But in terms of sheer quality of construction, the classic M3, with its projected, parallax-compensating, auto-indexing 50, 90, and 135mm finder framelines and 68.5mm-base, 0.92X finder magnification, is still unsurpassed in terms of actual field performance and as an object of timeless beauty.
It's like butter
The Leica M3's controls operate with silky smoothness, and it's been universally hailed as the camera that fits your hands better than any other--and as the prime tool of most of the renowned photojournalists and street photographers of the last 50 years. Its horizontal, cloth, focal-plane shutter is also whisper quiet and provides mechanically timed speeds of 1-1/1000 sec.
Double-stroke (two very short strokes to advance the film to the next frame)