Most/many South American countries were in fiscal chaos in the 1970s. Currencies inside the countries were often pegged at artificial exchange rates while outside the countries on the open money markets they were in free fall. There were restrictions on holding foreign currencies. There were restrictions on bringing domestic currencies back into their countries of origin - nobody wanted their own currencies back. There were restrictions on imports in an effort to stop money flow out of the countries and to try to address huge imbalances of trade.
Black markets thrived. US Dollars and Deutsche Marks could buy anything.
My mom came home from shopping one day, and my brother was doing his high school math homework at the kitchen table. There was a story in the newspaper that my mom had brought home about the currency collapse in a neighbouring country. My brother had a small stack of that currency left over from a trip there. My mom had also bought toilet paper. My brother went and got his leftover currency and did some measurements and math cost analysis - surface areas - TP vs currency vs costs. It was cheaper to use the currency from the neighbouring country. It's nothing that hasn't happened elsewhere, say in the 1930s, and it is something that could well happen again. (For a variety of reasons I am being purposefully vague here.)
It makes sense that the pedals would be made in Argentina. By making them there, import restrictions on components could probably be waived. There was probably hope that the pedals could be sold outside both locally and outside of Argentina. Musicians, without families with power/political/military connections, were starving for gear all over South America. Trade between South American states was perhaps easier than trade with North America or Europe.
It would not surprise me if the Guild name was used illegally, but counter to this is the question, why? Guild was not well known in South America in the 1970s. Fender and Gibson were. It would have been far more lucrative to rip off their corporate logos.
Whatever ... whether of questionable brand legality and/or questionable quality or not, the pedals would most probably be found in the major cities of South America (if indeed they were actually made in Argentina). Facebook Marketplace seems to be more active there than Craigslist.
I would imagine that even Guild knockoffs would have their own idiosyncratic attraction to the right collector.