The pin catches on the choil and prevents the knife from being withdrawn until it is released. The sheath was originally designed for the TT model, but the mil model fits just as well. I was worried because the tolerances are pretty tight. It matches a pin lock model I have for my Busse Meaner. On that one it locks into the talon hole and is really secure.

I think the inlay is simulated crocodile/alligator. It was originally going to be cane toad, but he was having trouble getting some in a timely manner, so plans changed.