Over 2500 bronze mirrors made either in China or Japan have been excavated from Japanese tombs of the Yayoi and Tumulus periods. Chinese mirrors differ from the Japanese ones in style, manufacturing techniques, and composition (Chinese: 60-75% Cu, 17-30% Sn, and 3-7% Pb; Japanese: 70-90% Cu, 2-20% Sn, and 3-8% Pb). In an attempt to distinguish the two types by analysis without sampling, Sn/Pb ratios were determined by analyzing 1.5 cm spots on the surface with x-ray fluorescence. Results correlate well with those from wet analysis and those previously reported. While the two groups overlap where the ratio Sn/Pb is about 2.0-3.0, the provenance of about 80% of the mirrors can be quite reliably distinguished.