Morse Int'd Thread USN Mark III Helmets in History Challenge Coin (Series Set #3)

The fourth in a series of limited production collectible “Helmets in History” challenge coins produced for and sold by the Historical Diving Society USA. Each coin in the series will highlight a diving helmet with a positive impact on deep sea diving.

Every coin produced has the original HDS logo of an Augustus Siebe helmet on one side and the featured “Helmets in History” helmet on the reverse. This coin features the U.S. Navy Mark III helmet.

These collectible coins are 1.75 in diameter, are highly detailed, and will be a prized possession for years to come. Each comes in a soft PVC envelope.

After the publication of Gunner G.D. Stillson's "Report on Deep Diving Tests-1915", the U.S. Navy followed through on the recommendations contained and the famous Mark V was introduced into service. It became necessary to designate different styles of earlier helmets. From the U.S. Navy's 1916 Diving Manual; Interrupted screw type; otherwise the same as Mark I.

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