Without digging out my books, the Ballester-Molina (at first called the "Ballester-Rigaud," Rigaud & Molina being individuals associated with its design and manufacture) was introduced in 1938 to supplement the existing supplies of Colt-produced Modelo1927s. With WWII, supplies of further Colt pistols would not be forthcoming, due both to US needs and to Argentina's neutrality.
After WWII the Argentine military obtained a license and equipment to manufacture M1911A1 pistols indigenously as the "Sistema Colt." The Ballester continued to be manufactured in parallel.
There's no relation between the Ballester and the Colts beyond a superficial resemblance. The Ballester uses the Star-type lockwork. While the barrel and magazine are generally interchangable, as stated earlier that was likely a matter of convenience for the former and a necessity for the latter, if the pistol were to serve in the Argentine police and military alongside the Colt. You couldn't have two .45 pistols with different magazines; imagine the confusion.
The Ballester is a good pistol in its own right, but should never be represented as anything like a Colt. I have a first-year Ballester (-Rigaud) and several others, including an Air-Force marked -Molina and a .22LR "Colt-Ace-type" variation.
Author, The M1911 Complete Assembly Guide,
The M1911 Complete Owner's Guide,
The M14 and M1 Garand Complete Assembly Guides
and The AR-15 Complete Assembly and Owner's Guides