This can be Error stamps or Freaks stamps or Oddities stamps also because it is one of a kind if genuine.!!
Do you really think this is ERROR stamp or Oddities stamps?
Of course it look like Error stamp or Freak stamp, but can you believe it.?
Do you really think this Error stamps or Freaks stamps or Oddities stamps was sold by postal administration as it is registered cover ?
This are imperf stamp which has missing black color, so you don't see detail like country name and other details on the stamp.
But still it was not notice by postal administration and they applied rubber stamp on it.!! They need to make sure which country it belong too even though it is look alike.!!
Do you really think this is genuine used ?
Click following link to read my other blog post related to this kinds of Error stamps Freaks stamps Oddities stamps.
Hungary stamps : Is this really error stamp used on cover ?
Imperf Stamps - Imperforated stamps