Here's the latest addition to my government check collection. Each quarter, local postmasters would issue these to contractors for transport of the mail. There were very specific instructions on the backs for both the contractor and the postmaster.
Just got this one today. If you look closely you'll find two banknote imprints, National Bank Note Co. at the bottom and a monogram of ABNCo at the feet of the vignette. American BNC assimilated National in 1878, so they just added their logo to these checks when they reprinted them a few years later.