pre ww1 just rare, lots of commercial 1911s saw service in other armies (1916 Commercials almost all went to Russia, UK, France..) very few statyed state side! pre ww2 the hand fitting, the beautiful finnish. They are the old style guns. Post WW2 Colt changed the production methodes and the guns are of another generation, they learned a lot on production during WW2.
Before WW2 Colt 1911 and 1911A1s used nothing but machined steel parts, and since labor was cheap there was a lot of effort placed in making guns that were cosmetically PERFECT. If you ever get a chance to look at a pre-war Colt closely, you will notice that all the exterior surfaces are devoid of any tooling marks or uneven edges. Cycle the gun and you'll feel absolutely no grittiness, but instead the feeling of polished metal riding on polished metal. This of course is regarding the commercial guns. Military guns will show more roughness (contract guns a LOT more roughness), but they still used machined parts and have the added benefit of being collectible pieces of our nation's history.
That being said, there is nothing wrong with a new M1991A1 and all its stamped or plastic parts. They're just boring, that's all.