My two 3rd Generation Colts.
The top one was unfired when I got it. I tried to take it apart once, but stopped when the barrel would not separate from the frame (with the force that I was using). Not wanting to mar it in any way, I stopped and let it just sit there looking pretty. Then I got an email from a collector who had seen the pic online somewhere and he offered me X amount of money for the gun - over a grand. We went back and forth for months over the price, then I decided that I did not want to sell it. Instead, I took it out and fired it (18 rounds). It shoots as well as it looks. What a great gun. When the collector heard that I had fired it, his offer dropped by over $200. I still have the gun. I took it apart to clean it - the reason it had been so "stuck" was the hardened factory grease. Now it comes apart with minimal force, and is as tight and smooth as any gun I've ever owned.
The bottom one in the pic was fired when I got it but still fits together nice and tight. It's a great shooter - it actually spits out the spent caps like a semi-auto ejecting empty cases. I have studied it to see what actually makes that happen but cannot figure it out.
I have original guns that I shoot, plus Piettas, Ubertis, a Santa Barbara Remington (recently sold but I fired it), and I gotta say, these 3rd Generation guns are amazing. But they do come apart with some difficulty compared to the others. I would never put a conversion cylinder on either.
Your fluted 3rd Generation 1860 is a beauty ( as are the other two).