Overprinted REVERSION / CONCESION MARES / 25 Agosto 1951 in black on SN 468.
Even though there were attempts as early as 1941 for the Colombian government to legally take over the Tropical Oil Co., it wasn't until the legal end of the contract of the Concesión De Mares expired that a transfer of ownership could take place. The reversion of "De Mares Concession" to the Colombian State on 25 August 1951 gave way to the Empresa Colombiana de Petróleos, which had been created in 1948.
