If it helps at all, I know some electronic pieces have a 45 degree cut on one corner so that one can orient the part the right way. So, not to say it's an electronic part, but it could have been something that needed to be assembled "the right way". Or, it could have just had the corner clipped off. Hard to tell without having it in hand. Since it's made of a metal that conducts electricity relatively well (I think), my guess would be that it was some sort of junction or bus rather than a wire guide, since I would expect most wire guides would work better when made from an insulating material. I'll be interested to hear what others have to say though. A curious find indeed!