Government Model is a pistol produced for the commercial market
by Colt, regardless of whether or not it has the 1924 improvements. These pistols will have a C prefix or suffix with their serial number. The C is considered part of their serial numbers, and should be included when making reference to the serial number of these commercial pistols.
M1911 is a military model designation for military pistols shipped 1912 through 1919
, and only refers to pistols produced under contract for the United States Government. Serial range is 1-629500.
M1911A1 is a military model pistol produced in either 1924, or 1937-1945.
Serial range is 700001-2660318 and only refers to pistols produced under contract for the United States Government.
The military M1911 and M1911A1 pistols do NOT have a C prefix or suffix with their serial numbers. They do have an No (o is underlined) or NO. serial number prefix before the serial number.
The first M1911A1 military pistols were produced in 1924, but were originally designated the Improved Model of 1911. Then in 1926, the M1911A1 designation was approved and made retroactive to include all military pistols produced back to 1924 beginning with serial number 700,000...although the serial range actually began at 700001.
Colt's specifically picked the name Government Model for their commercial series of pistols in order to boost interest and sales by promoting the idea that it was the same basic pistol that had been accepted by the U.S. military.
There are other specific differences by year and serial range in the finishes and characteristics of commercial Government Models and military M1911 or M1911A1 pistols. Those differences may be more difficult to distinguish, but anyone can determine what type of pistol they have with this information.