On the subject of the T-slot receptacles (meaning the old style with both sides a T-slot, not just one as with 5-20 and 6-20 NEMA types), I've wondered how and why these came into being.
If both 120 and 240V appliances could be wired with either parallel or tandem plugs at one time, it seems like it could have been a disaster waiting to happen for someone.
