Above is a drawing of the original Arriflex 16S (the S stood for Standard) which was introduced in 1952. During its production run, there were over 20,000 of these cameras made. As you can see from the picture above, the camera changed little in appearance over the years, but there were some significant improvements. Let's take a look at them.
The original cameras had a "flat door" and the Zeiss viewfinder, as seen below.
The back of the camera had a ribbed design where it met the magazine attachment.
Inside the camera, the sprocket guard had no rollers, and the springs that drove the feed and take up spools were exposed.
The divergent rotating turret of the original camera had three aluminum ARRI Standard mounts.
After approximately camera number 5600, the Zeiss viewfinder and "flat door" were replaced by the "beveled door" and the more modern viewfinder, and the front (door side) of the camera took on the look it had till the end of production.
The rest of the camera stayed the same until approximately camera number 8000, when the sprocket guard acquired two rollers and the exposed drive springs were covered.
At about this same time the ribbed design on the back of the camera was changed to a smooth design.
With the introduction of the Arriflex 16S/B, a steel ARRI Bayonet mount replaced one of the aluminum ARRI Standard mounts in the turret and a turret lock was installed.
And finally on some of the last Arriflex 16S cameras made, ARRI installed an APEC (ARRI Precision Exposure Control) system.