The seller of this gun IMO is mistaken in his belief that this gun was purchased by the Military. Kopec covers these in his book with a logical explanation. Whenever Colt got an order for 44-40's and they had none in stock they were not beyond yanking barrels off of .45's in house & fitting 44-40 cylinders. IMO, this is probably a rejected military frame that was in house and they fitted an etched barrel & 44-40 cylinder to fill an order. Victorian era manufacturers were very thrifty. "Waste not, want not."
Also, notice that it was shipped to Schuyler, Hartley & Graham as well. These are not common today. Enjoy.
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=210361828