The tug depict on this stamp has the inscription RDA, not a tug exist so far I could find out under that name in Cuba.
R.D.A. means Republica Democratica Alemania (East Germany, DDR) Remolcador is Spanish for tug.
Most probably the tug was a present of East Germany to Cuba.
Have not any info on the tug.
Cuba 1965 10c sg1315, scott1062.
Sources: EWA.