The footnote under Scott 432, which applies to all of the privately printed issues of the time including this set, says:
Quote:
Many so-called "errors" of color and perforation are known.
The blurriness of your stamp indicates it's a reprint, and apparently one of the "errors of color" that the printers produced, too.
It's in the same category as the inverted vignettes on some of these issues, intentional errors made for collectors. Still, no collection of Spain would be complete without oddities like these.