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.
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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