Argentina 1935-51 8 centavos value

From the specimens and usages available, it is unclear to me which postal rates were intended. The 8 Centavos is found on various philatelic covers. Below are two mint specimens and an used specimen. There are slight variations in color. Here are quick links to the "cents" section, the 8 centavos design page, the 8 centavos issue page, the 8 centavos plate varieties page, and the "cents" covers main page.
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