Interesting ideas everybody, thanks. The hardness tester idea is a good one but this item was in a pouch just big enough for itself and I would expect instructions as well as ancillary items.
Clive I have to be honest, that's a new one on me, and even after a quick Google it looks way over my head. But for that reason it could well be a possibility for all I know.
The engraver idea seems the most plausible, the drag engraving tools certainly share some resemblance it's just, as said, this item seems quite a bit bigger. It could have been used on a large machine though I suppose.
Thank, Craig