Always suspected philatelic uses, we will never know.
This first one IS philatelic, a local Argentinean use.
"Samples without value" 26 centavos postage. Likely not philatelic.
Slogan 15c ship rate.
The 8 centavos is usually found on philatelic covers.
15 centavos rate that would have usually been posted with either three 5 centavos Moreno or one 15c small-format Cattle (15cSC) stamp.
