The Uberti hammers are cast. And even the checkering almost smooth by comparison to milled or hand cut. It is pretty obvious. The USFA hammers are milled or hand cut, and the checkering sharp. Also pretty obvious side by side.
The USFA milled/hand cut hammer you show in the picture is considered a Colt 1st Gen style hammer serration and is not a Uberti part. Hammer serrations are a clue on what might be a "parts" gun. But one must know what you are looking at..cast or milled.
USFA had several styles, at least 2 major ones (may be 3 or4, I'd have to look and count) of checkering/serrations on the hammers they used with USA production that I know of. I believe I have samples of them all. Not sure on the other firing pin style but it may have been used in limited numbers as well. But all the USA hammers I own (in guns and spare hammers) have the cone style firing pin.
I know Gary mentioned changing some firing pins out because of primer flow. Which would confuse the issue even more if the gun was a parts gun to start with and a cone firing pin added or a USA gun and a tapered pin added. Lots of details to figure out what parts are actually in these guns in the transitional numbers. Seeing a cone firing pin is likely the most definitive way to avoid a Uberti parts gun.
I have posted a picture of a pair of Rodeo IIs prior with USA, 1st gen style hammers, cone firing pin, that are case colored. Same as what you have pictured here. It is a nice detail.
Also worth noting if you are into the details. The blued hammer's checkering with polished sides are often (always?) not as sharp as the nickel or case colored hammers. One might think they are cast because of it. The issue seems to be the fact that the finisher over polished the cocking serrations prior to blueing. They started out sharp, then were dulled during buffing prior to blue. Seems the color cased and nickeled hammers didn't receive such unwanted abuse
Sharp checkering on the hammer and lots of it, makes thumb cocking with the shooting hand a pleasure.
I find the detail worth the effort enough to even have my Colt's hand cut to the original 1st Gen style serrations.