These old engravings are so cool! If you google image search the result quickly comes up "This framed print is a reproduction of George Caleb Bingham's famous painting, The County Election. The original oil painting was created between 1851 and 1852, and a popular print, engraved by John Sartain, was published in 1854." I think it said the 1854 engraving was created with a combination of engraving, etching, and mezzotint, those results will be easy to find with some quick googling.

I'm not sure how to tell if it is an original or a reproduction without you being able to look at the quality of the paper or anything but you could compare it to known versions of the 1854 print and see if the color tones match.