Having access to enhanced resources I have run a few searches through the educational database. Here is an article you might enjoy. As nickel, and pure nickel, have been secondary discussions on RealCent this article was both interesting and informative.
Abstract: Perkins, J. (1992). coins for conflict: Nickel and the axis, 1933-1945. The Historian, 55(1), 85-100. doi:10.1111/j.1540-6563.1992.tb00887.x
This article explains how the Axis powers preparation for the Second World War began as early as 1933 to stockpile nickel as a strategic metal. Nickel is the best hardener for the manufacture of steel. The Axis picked a primary place of storage of pure nickel was in circulating coinage. Although copper-nickel coins look like nickel until the percentage fall below the 16% threshold, the Axis powers made pure nickel coins. Switzerland was the first country to make 100% nickel coins in 1881, setting the precedent for others to follow including Germany, Japan, Italy, Canada and France. The article discusses most of the nickel active nickel mines were in Allied Territories. When war broke out and the coins were recalled the result met most of the Axis need for nickel. The recall of coins was effective, for example, in Japan although “almost 360 million nickel coins were produced,” “only 2 of the 5 Sen pieces survived the recall.” There were some in the Allied Powers who noted the pure nickel coins could be used for expedited arming, but no action was taken.