Today's history lesson.
If I showed you this image, how many would know who he was and what indirect connection he had with US stamp and cover collecting?

The fact is, he was a Philadelphia-based stationer and included among his inventions was the first pencil with a rubber eraser on it. Beyond that, included in his obituary was this comment he made sometime earlier about his invention(s) in manufacturing the first gummed flap envelope in the US and having the printer of the first US stamps come to him to learn how to make the mucilage (gum) used in affixing stamps:

Somehow, Wiki doesn't seem to do him justice:
http://en.wikipedia.org/wiki/Hymen_Lipman