I believe your rightmost stamp is a postal forgery.
For the postal forgery:
- The "C" of CORREIO is squared off at top and bottom and is slightly larger than the rest of the letters.
- In the crown of laurel leaves, the leaves are slightly larger and whiter (shading different and not as heavily drawn)
- The "corner" design at upper right is clearly separated from the scroll
- The bottom right "REIS" has thinner letters, most notably in "S"
There are more points but are obscured by cancels here, or overinking. These characteristics are also true for the bicolor 100R, 200R, 300R and 500R postal forgeries.
EDIT:The most obvious is that the genuine was printed in two steps typically with two different shades of blue, though sometimes hard to distinguish. This postal forgery was apparently only printed in one step with one shade of blue overall.
Additionally, the postal forgeries are known used around 1900. If the lowest "9" in the cancel means 1899, that fits also.
This is not a rarity but is relatively scarce.