Is mine a mixed pistol like the one on this thread? I'm sorry but I just can't see the difference on the slide. Any help is appreciated.
With the commercial model of the 1911A1, you would definitely have all the "updates" (like the scalloped frame, lowered and flared ejection port, etc.). The commercial model was made specifically for sale on the retail market and would never be pieced from old 1911 parts.
The U.S. PROPERTY guns, however, is a different story. There were (depending upon the date) many pistols that were pieced together (i.e. 1911 slides and 1911A1 frames) and these are called "transition" pistols. Many were rebuilds by the military's armories. Again... it depends on the date the pistols were placed into service.
Without being able to look closer at the markings on your Colt, I'm unable to tell if it is one of those "transition" guns or if it is a "Frankencolt". Chances are though that it is a 1911A1 with a replacement slide from a 1911. Another feature to look for and that helps with identification is the finish on the gun. Depending upon the year of manufacture, there are several different types of finishes that were used.
Hope this info is helpful.
lawdog