The Southern Methodist University (SMU) has digitized a collection of Baldwin Locomotive Works engine specifications from 1869 to 1938. Below is a scan of the page for Niagara Junction Railway locomotive #2.
It is designated as a class 4-28C. The leading “4” indicates the total number of wheels, the “28” is the size of the cylinder, and “C” indicates there are four driving wheels. Therefore, it was a 0-4-0 locomotive. Trains magazine has a good article on how to decipher Baldwin classes.
Some rosters list this as a 0-4-0T locomotive, indicating that it had a tank over the boiler for water rather than having a tender. This record shows it having an 8-wheel tender holding 1150 gallons of water.
The locomotive had the name “Niagara Junction Railway Company Co.” painted on the tender, “N. J. Ry. Co” painted on the cab, and the number 2 painted on the dome on top of the locomotive, on the back of the tender, and on a number plate on the front of the locomotive.
Source: Baldwin Locomotive Works engine specification, volume 19, page 40 (page 42 of the PDF file). From the collection of Southern Methodist University libraries.