The black 5 centavos is common and listed in the Celico catalog as "Revenmue-Postal stamps" as number 1. Cefilco values it at $1.00 US though they are real common and almost valueless (I have part sheets). If postally used, it values it as $2.00 and revenue use at $0.50. Quantity issued was 1,600,000.
The complete set is five values going up to 500 centavos. That one is valued at $100 USD mint and $50 pen cancelled (revenue use).
The Cefilco catalog explains them this way: Put into circulation en the country as revenue stamps from June 1866. In August 1867 a decree was issue that give provisional use as postage stamps as adequate supplies of regular stamps were not available.