My "gut feeling" is its military. Sorry not be more helpful.
Well spotted, you have a sharp eye.
I'm sure I saw similar ones on ebay..seller stated they were German issue?
Thanks chaps, until I know otherwise it can go with my medical kit.
I'm pretty sure you're correct, a Tourniquet...I agree with NCA, as I clearly recall a Bulgarian Ebay Seller offering them among other medical supplies...
Just a follow up on this thread, I have found confirmation that these tourniquets were used by the British military. this illustrationis from a 1930 copy of the Royal Navy's 'Mannual of Instruction for Sick Bay Staff':