Regarding Uberti Cattlemen in general, or Cimarron Model P in particular since I'm most familiar with that importer. Old Model just means "BP Frame" with the screw in front of the frame retaining the base pin and the bullseye ejector head. Also V-notch rear sight and tapered front. The internals are the same on Pre-War and Old-Model (all have the coil hand spring, for about 20 years). When you look at some of Cimarron ads, and they mention the "Cowboy Comp" action, they are talking about the coil hand spring. Used to be a Cimarron exclusive for a number of years until Uberti standardized on it.
As for the Pietta vs. Uberti 7th Cavalry, I'm not positive right now since I haven't seen a Pietta model in a couple years, so they might have changed, but the Piettas had less of the markings. At first there was no Company letter, no matching s/n on triggeruard and butt, nor "v" mark on cylinder, etc. They did have the grip cartouche and U.S. marked on frame. I think since then I saw online where someone had one that had some of the markings added. Also, I seem to recall Pietta BP frame pistols having the squared off sights, but not sure if that is still the case either.
Regarding bolt/trigger springs, most Model P's and standard Cattlemen have the flat spring. Some Uberti competition models such as El Patron mentioned, I have no idea, but wouldn't doubt a wire spring (the Evil Roy Model P's have a flat trigger/bolt spring). The stainless Model P's do have a wire trigger/bolt spring. At one time I also saw some wire springs in the small frame Lightning/Model P Jr. guns, but they went back to flat.
So, about Medic15al's missing coil spring, I don't know. Possible theory: Since the Cimarron Old Model P is currently the only version of Uberti's cattleman with the standard 4-click hammer, perhaps they are using up some old frames they had in stock to make those guns? But they would be REALLY OLD frames, so I really have no idea. And there is no difference in the frames between the 4-click hammer and the Cattleman II with the telescoping firing pin, so I don't know why they'd need to use old frames. A mystery.