Take apart dorcy hawkeye?

I cant for the life of me unscrew the head of the flashlight. I want to me able to put my aixis module and circuit board in there. With this flashlight do i need a board?
how do i take apart this sucker?

If it's screwed on, how about gently grab it in a vicegrip and twist it? I know the words "gently" and "vicegrip" don't go well together but you can use a piece of cloth to avoid scratches, and don't squeeze it very hard to avoid making the head oval