Of course this may be anything but real bronze but let us assume it is assayed as a creditable bronze.
Again, the little that I can see suggests only more recent sources. This is however an artifact of the usual problem of archeology. That is, it was not there, so do not dig so deep and that copper was money. You paid your taxes with it. That meant that copper produced in 4000 BC was reworked over and over again until it hit 1492 as something almost recent.
Any way, bronze alloying was clearly understood in the Andes. They do not mention age so we can assume that it was recent because it is identified as Inca.
Once again lack of evidence is not evidence of lack. Now if we could determine if the Bolivian tin mines were worked in pre Columbian times.
After saying that, I located a paper written back in 1915 that essentially confirms the full development of bronze technology and the use of refined tin for its manufacture. The copy on the internet is an OCR of a scanned document and tables and illustrations are trashed as are footnote numbers.
I cleaned it up as best as possible so that you can at least read the text. The visible technical expertise is excellent. These guys knew their way around an assay lab.
The take home information, contrary to published position in far too many books that we are expected to rely on is that a fully developed bronze making culture, directly equivalent to the bronze making culture of Europe existed. Proving it is ultimately contemporaneous is a task of digging deep enough at the right place.
Again recall just how much digging has been required to collect the few artifacts that we have found in Europe. This stuff was money and if they did not bury them as grave goods, we have a problem.
I have added the reformatted and edited version of the paper at the end of this blog as the original copy is a mess.
277 bronze artifacts found at Archaeological Park of Sacsayhuaman
277 bronze Artifacs found at Archaeological Park of Sacsayhuaman located in Cusco, Peru. Photo: ANDINA / INC-Cusco.
Cusco, Dec. 17 (ANDINA).- Skilled workers and professional staff of Peru's National Institute of Culture in Cusco (INC) founded 277 bronze artifacts (champi) when conducting archaeological research at the Archaeological Park of Sacsayhuaman located on the outskirts of Cusco
179 plumbs (cylindrical cone-shaped weights) of different types and 98 nose rings were discovered inside the enclosure No. 06 of the archaeological site of Inkacárcel that, according to preliminary investigations, was a warehouse or "qolqa".
The director of the archeological park, Washington Camacho, said that these artifacts were found with decomposed human remains, and burned products such as corn, among others.
He highlighted the importance of this discovery, which would confirm the hypothesis that Incas had different methods of construction used to build their houses, and employed high-quality techniques to control vertical alignments of their buildings.
Full text of "Prehistoric bronze in South America"
ANTHROPOLOGICAL PAPERS OF THE American Museum of Natural History.
Vol. XII, Part II.