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3/16 of an inch; this was the total thickness of Dowmetal that protected the balloonist from the uncertainties of the stratosphere during the the 1934 and 1935 National Geographic Society - U. S. Army Air Corps Stratosphere Balloon Flights.  The Dow Chemical Company in Midland, MI touted their magnesium alloy as the "World's Strongest Light Metal" (it was only two-thirds the weight of aluminum and less than one-quarter that of steel) and for that reason, the Explorer Gondolas were constructed of Dowmetal.  The spherical shape of the gondolas would allow stresses to be uniformly distributed.  The gondola constructed for the 1934 flight was 100 inches in diameter and only weighed about 700 pounds empty.  As described in last week's discussion, this gondola was destroyed during the 1934 crash of the Explorer Balloon.  The gondola constructed for the 1935 flight of Explorer II was 109 inches in diameter, but weighed only 637 pounds empty.  The decrease in weight was realized when shelving used to support the weight of scientific equipment used during the 1934 flight was eliminated.  During the 1935 flight of Explorer II, the scientific equipment was bolted directly to the side walls of the gondola.


Pieces of the Explorer Gondola have been on display at the United States Air Force Museum in Dayton, OH for several years.  The Explorer II Gondola is on permanent display at the Smithsonian Air and Space Museum in Washington, D.C.


In order to promote their part in the Explorer Balloon Flights, Dow Chemical produced commemorative coins (tokens) made of Dowmetal.  The tokens measure 1 3/8". Examples can be seen in the attached photo.  Typically, the tokens are extremely oxidized and nearly black (as shown in the middle example) when offered for sale.  Using proper cleaning agents, the oxidation can be removed.


For many years, Dowmetal Explorer II tokens were considered extremely rare and sold for as much as $1000.  Ebay and the discovery of a cache of the tokens have considerably decreased their value.


In next week's installment of The Souvenirs and Collectibles of the National Geographic Society - U. S. Army Air Corps Stratosphere Flights, we will discuss NGS Presentation Flags carried on the flights.

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The photo used for the May 1936 supplement was on taken November 11, 1935 during the flight of the Explorer II Balloon .

Charlie Gannon
Here is a Kodachrome photo by Bruce Dale (circa 1950's?). It shows the Explorer II gondola located in the Society's Explorers Hall.

Rear of postcard states:

"Explorer II held the world's altitude record -- 72,395 feet -- for 21 years. In a 1935 expedition sponsored by the National Geographic Society and the U.S. Army Corps, the gondola carried Capts. A.W. Stevens and O.A. Anderson 225 miles across the Black Hills. National Geographic Society in Washington, D.C. exhibits this gondola."

I am not sure of the date (when this post card was published; or when the actual image was photographed by B. Dale). Any guesses?

In your article you mention removing the oxidation, which process has best worked for you?


The quickest way is to dip the coin in an acid solution, preferably hydrochloric acid. I use a toilet bowl cleaner called The Works. It has about 9% Hc acid. I put just enough of the solution in a small acid resistant cup to cover the coin. Just a couple of seconds is all it takes. The coin will become very hot, so run cold water over the coin to delete the acid and cool the coin. Wear all necessary projection. Repeat if necessary. Keep the coin in an air resistant case and it will stay shiny for years.

Good luck.

Awesome your my hero worked like a charm! It was so dark it wasn't ledgable Now I can actually read it and display it. Thanks for sharing your knowledge Charles

You are welcome.



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