Don't think it's a preform, but definately a tool. I'm learning as I go, but so much stuff just isn't definable. I generalize and just say...it's a tool...no doubt about it. IMHO.
They would make preforms when at the flint quarries in order to make it more portable. The Preforms would then be put somewhere in a cache for safe keeping or would be finished out into projectiles of various sorts.
You know, I have a couple spear heads that are nearly that size. I would say that it IS worked along the edge for sure, but it is hard to tetll from a photo.
There's no doubt at all- it's a Hixton preform, maybe hard for some to tell if you're not familiar with the material because it doesn't show the flaking scars very well but let me tell ya- it's pretty stuff in hand.