Indications Point To Calendar Year. Source: History Of Baldwin Locomortive Works, 1832-1923 P. 182.
This NBER data series a01151 appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: a01151
Release: NBER Macrohistory Database
National Bureau of Economic Research, Locomotive Production, Baldwin Locomotive Works for United States [A01151USA481NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A01151USA481NNBR/, September 3, 2015.