Six pieces of prototype hardware designed by Pratt & Whitney for the Apollo Lunar Excursion Module (LEM) Fuel Cell, comprising two electrode frames, two gas plenums, and two halves of the nitrogen jacket. The nitrogen jacket halves were electron beam welded along their outer perimeter seams, and have half-inch holes at the bottom where the nitrogen pressurized gas manifolds came through to pressurize the cell; these manifolds ran along the bottom of each side of the fuel cell stack. The fuel cell was composed of two side-by-side fuel cell stacks, which in series together gave an output of 500 watts at 28 VDC. NASA ultimately decided to use a battery, rather than a fuel cell, to power the Lunar Module, and the contract with Pratt & Whitney was canceled in 1965. In overall fine condition. Accompanied by a blue Pratt & Whitney box and a three-page letter by engineer Ted Koch discussing this hardware and the LEM Fuel Cell project in detail. In the letter, he states: "The pieces which are enclosed are probably the only LEM Fuel Cell hardware items left in existence."
