Platinum and platinum-gold metallurgy was fully developed by smiths in the Esmeraldas-Tumaco Pacific coast area of present day Ecuador and Colombia long before the arrival of Europeans in South America and centuries before platinum metallurgy became practicable in the Western world. Using gold to sinter together nuggets of native placer platinum, then alternately working and annealing the resultant solid, these South American smiths produced hard, fairly homogeneous platinum-gold alloys of a range of colors for fabrication into items of adornment, and small tools, such as needles, tweezers, awls, and fishhooks. The microstructures and compositions of sintered platinum-gold objects from La Tolita, Ecuador, and of experimentally simulated platinum-gold alloy samples were analyzed using new electron probe microanalysis (EPMA) techniques and data from the platinum-gold phase diagram in an effort to determine the fabrication temperatures used by pre-Hispanic South American smiths. A comparison of EPMA results from the simulated materials with the corresponding results from the La Tolita platinum-gold objects suggests that the platinum-gold objects were never heated as high as 1100°C and probably never contained a liquid phase. As illustrated by this comparison, the qualitative and quantitative information provided by these new digital acquisition and display techniques far exceeds what conventional line scan and x-ray dot maps could provide.