The first variant (Koll's versioning numbers) is the easiest of the 314S's to identify.  Like the other tank models produced in the years leading up to 1950, the V1 has two principal features that help to classify it. 

The first is the the presence of a wire brake rod or "Bremsspindel" in German.  On the brakesman's cabin end of the car notice the wire rod that extends down from the middle of the cabin to attach to the chassis.  Later versions do NOT have a wire brake rod - rather the rod is molded into the cabin casting.  It has been suggested that the wire was removed as a cost saving measure.  Also note that the cabin window is punched out in the first version and it is closed (covered over) in later versions. 

Using the pointer of your mouse (or your finger if using a touch device [tablet or phone]) drag the arrows to the left and right in the accompanying interactive image to note the above differences.  The image on the left (as indentified by the label) is the first version and the image on the right is representative of later versions (version two in the example)

The second principal feature that identifies the first version from later versions is the presence of the Kolls Type BK 4.2 coupler, often called the "hook" coupler.  Later versions of the 314S all were fitted with Kolls Type BK 5 couplers.  Note the differences in the image below.

The main features that identify a 314 S version 2 are the previously mentioned lack of a wire brake rod (present only in V1) and the use of Type BK 5 couplers.  It is worth noting here that a version 2 (like a V1) does NOT have brake shoes or "Bremsbacken" (German).  

Using the interactive image to the left note the difference between a car that does NOT have brake shoes and one that HAS brake shoes.  The image on the left is from a version 2 and the image on the right is from a version 3.  Note that the brake shoes extend down from the chassis on both sides of the wheel and would grab the wheel at a 9:00 and 3:00 o'clock position would they be functional.  Obviously in the model they are non-functional and merely cosmetic. 

The 4th and final version of the 314S also had brake shoes like it's predecessor,  but V4 is marked by the presence of a tube that attaches the tank to the chassis.  Evidently the tanks with the attachment tubes were not ready for production at the same time as the prepared chassis and this resulted in version 3.  Version 4 was only produced in 1955.  In the interactive image to the left note the tube that connected the tank to the chassis.