It's - ahem - phallic.

That fact aside though, it looks as if it was cut from a generic blank lug. Note the slight angle to the socket at the front - it hasn't been filed off, or filed round. I can't think of it at the moment, but I've seen at least one other lug with this same edge to it, unfinished. Can't remember if this was on an English bike or a Japanese bike. I'd lean towards the latter.

-Kurt