I'm gonna have a go at it, I could be wrong in some places though.
The first L4s had 3 flat sides, when looking at it, the head pointed right and clip on the up side, you would be able to read 1st line:L4 Digital Lumamax 2nd line: Patents.
Note: I remember seeing it opposite also (head pointing to left) but I'm not sure where this one goes, just sure it was before the next one.
Note: Along the way, the FCC, CE and Caution Hot logos were added, in which sequence I dont' remember.
The next one had 2 slightly rounded/flat sides (if I recall properly was so that can be attached to something easier). When the head was pointed to the right, the clip couldn't be really seen cuz it was "underneath" and you would be able to read 1st line: Surefire 2nd line: L4 Digital Lumamax 3rd line: Patents.
The next one has 3 rounded sides so the body is essentially round and if you look from the back (switch) it looks like the sides forms a smooth triangle. The first batch of these bodies, with the head pointed to the left, the clip would be at the bottom side, you would be able to read 1st line: L4 Digital Lumamax 2nd line: Patents. This one didn't last too long.
The next one also had the same 3 rounded sides, but etchings changed. When the light head is pointing left, and clip up, you read 1st line: L4 2nd line: DIGITAL LUMAMAX 3rd line: patents. This I believe is the most current one.
To further this, the even newer ones, if you look directly on the KL4 head, the newest ones have KL4 written in italics, and the serial numbers smaller and non-italic. Before this, all of them had KL4 written in italics and serial numbers bigger and in italics also.
I've owned a few throughout and I believe output/tint have improved since the beginning.