Series Has Been Subdivided Into Two Variables: (1)-- Original Data, Lake Copper, 1860-1912; (2)-- Original Data, Electrolyte Copper, 1911-1955. Lake Copper Is From Native Copper Mines Of The Lake Superior District. The Standard Range Of Conductivity Is 99.5%. Electrolyte Copper Is Refined By The Electrolytic Process And Runs From 99.93% And Upwards For Cathodes. Source: 1860-1893:"Mineral Industry", 1893, P.253, And Following Issues; 1894-1955:"Engineering And Mining Journal", January 4, 1896, P. 5, And Following Issues (Also Available In "Mineral Industry" A Supplementary Publication Of "E & M Journal")
This NBER data series m04015a appears on the NBER website in Chapter 4 at http://www.nber.org/databases/macrohistory/contents/chapter04.html.
NBER Indicator: m04015a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Wholesale Price of Copper, Lake for New York, NY [M0415AUS35620M267NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M0415AUS35620M267NNBR/, November 28, 2015.