As stated above, most of the early New Model Army Colts ( up to about serial number 6500) were made with full-fluted cylinders, The idea was to reduce weight, and also equalize stresses in the chamber walls, an idea suggested to Colt by Wade Hampton of South Carolina.
Early on, there were problems with some cylinders blowing up, and Colt replaced these free of charge. (This would probably not be a problem with modern repros. :grin
Many of these early fluted guns were bought by the South, prior to the outbreak of hostilities. So they are considered secondary Confederate Martial Pistols. Four days after Fort Sumter was fired on, Lincoln called for troops, and Colt ceased all shipments to the South.
So, Alden, your gun is very historically correct - it was the original model first accepted by Ripley. And very beautiful it is, too.
The stud for a detachable shoulder stock was done away with, as not necessary for use of the stock. And the entire stock idea (Jeff Davis')fell by the wayside with the advent of countless repeating carbines for the cavalry.
I suspect the flutes were later omitted as a cost saving measure.
Most of the above information is from
Civil War Guns by William B. Edwards, Stackpole, 1962