As with just about anything and everything, there are collectors of the angled GI flashlights. Some are worth rude money- hundreds upon hundreds of dollars! I know a guy in Oregon that frequents the military vehicle shows with about 20 different ones, and all he ever looks for at thrift store and yard sales are those things. (The guy I run around with that has the militaria store here in Caldwell collects M1 Garand clips- and he is up to about 30 different ones with plenty he still doesn't have!)
I was told if you put all of the color filters in at the same time, it becomes infrared, but I have my doubts.