During the civil war of 1899-1902 (War of 1000 days) a series of provisional issues were made in parts of the country cut off from Bogotá: Cartagena, Cucuta, Tumaco, Barranquilla, Medellin.
In 1899 the Cartagena provisional government overprinted the 1c Seebeck issue of 1891 with wavy lines supposedly for foreign postings.

Cartagena to San Jose, Costa Rica
6 times the foreign letter rate of 10c -- 60c
Registration -- 10c
This is the only cover bearing this stamp that Bill Welch or I have ever seen. This is from Bill's collection. Do you know of another?