Hello Mike. I am not sure what goes on presently, with all the importation laws and such. There may even be a manufacturer here in the US that makes the FN under a different name. Look at Walther, Manhurin, Interarms, CZ, CZ-USA, and so on. I can't keep track anymore.
I do know that up until recently anyhow, FN was Belgian produced, period. These Buenos Aires Police are Belgium guns. They were simply sent to the FM plant in Argentine after they were replaced, for refurb and sales to the surplus market.
The confusion you see may have something to do with Argentina? The DGFM maker in Argentina cloned the Colt 1911 and Browning High Power for military purposes. At some point, probably in the sixties?, they dropped the DG and just went with FM. From my understanding, from this point on, the company began commercial sales as well as military. I would not hesitate to buy any DGFM-produced gun. In fact, I own a DGFM .45 Sistema and the quality is un-matched world-wide in my opinion. But, I do hesitate buying a current FM-produced gun, only because of it's "cloned" status.
So, as far as I know, and I may be wrong, FN has always been Fabrique Nationale in Belgium. FM is currently located in Argentina. Hope this helps?
Dave