My time machine will be completed next July. It will have an ignition switch that is activated by a barber's notch razor shaped key. When I go back in time I will lose my key, it will be found by a barber who will mail it to Wade & Butcher who will love the shape so much that they will start using the design for their razors.
So, you have me to thank for the barber's notch, but you don't need to thank me till the end of July.
I am relieved to put an end to the speculation.
Oh, and could someone remind me to carry more than one razor?