I made a post in Sosa's thread about the exploded battery in his Fenix light (nothing wrong with the Fenix), and got 3 PM's from people recommending I make this thread showing the images so people understand what a "Protected" & "Unprotected" Lithium battery looks like. If the moderators feel this is cross posting, please close the topic.
I sacrificed a Year Old (Current improved model has new features) of AW's 14670 cell to show you exactly what this means.
Click on the thumbnail images below. AW starts with a normal UNprotected cell in blue plastic which he also sells. These have the vent holes which help release pressure if the temperature rises, and gas expands. That means the starting blue, unprotected cell just has high temp venting protection (as far as I know).
Now note there is a thin computer chip on the bottom under a metal disc. One end is welded to the bottom (Negative Terminal) of the blue battery, and the other end uses a thin contact strip to run along the side and attach on the top Positive terminal.
It is this computer chip that does all the important sensing and interruption of the circuit, otherwise the blue cell is an unprotected cell. The additional black shrink wrap and label are added to keep the components anchored and insulated. You can feel and see the space at the bottom of the bottom of a protected AW battery where the PTC circuit is locate4d.
Please note AW's improvements on current version which parallel those of Pila in his post #9 of this thread. Excellent News because I have had a number of my Li-Ion's drop to the floor.
If the ones you are buying for other lights, such as R123 do not specify that they have this kind of protection, and especially if you don't see the circuit gap and feel the thin strip along the side, then it's pretty safe to assume you are not using protected Lithium cells. I hope this illustrates more clearly what a "Protected" battery actually means.
Finally, if I remove the blue wrapper you see the metal canister with the plastic circle on top that separates the Negative entire outside and the inner, middle top positive end. It is a shiny, stainless steel casing, it just photographed a darker color.