A recent pass through D.C. provided another excuse to endure all the security apparatus to see the U.S. Postal Museum on Capitol Hill. Most of you probably know that there is such a thing as a "national stamp collection" consisting of every U.S. stamp ever issued (although I saw only up through 2009 on display). The collection includes some pre-1847 postal ephemera as well. Everything is contained in a compact room that I'll guess is about 35 by 20 feet. Space management is achieved by employing wall-mounted sleeves, each about 48"x36": pull a slab completely out of its sleeve so that it can be pivoted on its hinge, et voila - a selection of mint stamps are mounted with brief explanatory captions. Photos are below - pardon my Zepp fetish.
The storage slabs:

A $1.30 Zepp plate proof:

A $0.65 Zepp plate block:

Jennies, etc:

A variety of philatelic fakes:
