Just a little update: I picked up the M-90 today. I have to say that I was expecting something very crude, and it turns out I have a gun that's practically flawless and looks to have been shot very seldom. Everything is still a little tight and there are no wear marks that I can detect. Finish is superb, all things considered. Not the beautiful bluing of the Belgians, but a nice military non-reflective black. The general consensus seems to be that the Argentinians are completely interchangeable. Although this gun wasn't made while the license was active, I understand that they were made on the same equipment with the same parts. I'll agree with jonnyc that it doesn't appear to be quite the same form and fit as the original, but the price was right and I'm happy to have the platform.
"Shut up, crime!"