I bet many people did see this effect by accident over the years, just by chance, but lacked the engineering imagination to realize its potential. That's the magic of an inventor's mind for you! Also, Olds &amp; Son is a great name for a workshop! Also also, amazing how sharp this guy's mind still is. I've seen people in their 30s and 40s with a duller edge.,(reply>), I´ve seen people in their teens with a duller edge.<br>No, wait - I WAS a person in their teens with a duller edge!,(reply>), Or 20s