I have one, nickel plated, delivered to the Governor's Island Arsenal, in early 1861, 3 weeks after the attack on Fort Sumter in a shipment of 200 revolvers, all blue.
I have owned it for over 25 years. It had been blessed as correct by Ron Ogan, Tom Haas and Herb Glass, Sr. who physically inspected it. While the nickel plating was determined to be a period New York plating since NYC was the hub of the gunsmith, plating, and engraving in that time frame, the nickel plate was usually done for Officers as an enlisted man could not afford this practical, protective finish instead of cosmetic appearance. For many years in the pre-internet day, I tried to determine why this 1860 Army was completely void of U.S. inspectors markings to no avail.
It was not until approximately 2010 I wrote Col. Charles Pate (U.S. Army, retired) wrote responded that my 1860 Army (SN: 51xx) was including in one of the first 2 U.S. Government orders (the 200 this one was included with was just a small part of the order), and as such the process of inspecting and marking had not yet been established as in subsequent orders.
Collecting Civil War related firearms is habit forming.