Cuban Stamps Help 1950

Help with the identification of three Cuban stamps. The stamps are of José Martí (1C), Máximo Gómez (2C), and José Antonio Saco (20C).

The design is identical to the "Patriots" series from the 1950s, but their characteristics are different.
The colors do not match the issued stamps.
They are not perforated. The edges are irregular and fibrous, similar to an old cut or separation.
They do not have a watermark (the star is not visible).
The paper is thick and has a cottony appearance.
The gum appears original (yellowish and shiny).
Vertical lines are visible on the paper.
They could be proofs, trials, printing overprints, or some experimental printing.
I would greatly appreciate any opinion or reference.

Thank you very much.

These are listed in Scott as 674-680 and issued in 1961-1969. There was some dispute about the birthdates listed on the original 1954 issues which accounts for the "?" which appears in place of Maximo Gomez' birthdate.

Thank you very much