Weapon of the Day - Holy Batman

So, as you all may know, weapons of over the ages take all types of shapes and forms. I came across the weapon below. I can not make heads or tails of it. For those of you in England, I call you out. This little piece of Batman-like weaponry/toolery just has me stumped. Of course I can find nothing more than entries by archaeologist's catalogues. So, since the dagger is found in England (isle of Wight to Yorkshire) and presumable widely dispersed and used, please explain it to me!

it looks more like a tool than weapon... of course...

linky