The stamp on the left above is the issued stamp. Our proof is on the left. As you can see, the denomination is different than the issued stamp.

This proof is missing the denomination. 

On the proof set to the left, all the denominations are different than the issued stamps.

The proofs on the left are mounted on a card with notes to change the denominations on the issued stamps. 

The two proofs above show 2 different denominations.
The proof on the right shows the issued denomination.
Both are pre-production proofs - please note the wide margins. These are not mass produced. They were printed as singles on sheets with other proofs.

Denomination different than issued stamp. Issued 20s

The proof on the left above has a different denomination than the issued stamp. The proof on the right has the issued denomination glued to the proof. Very unique.

The above proof from Tanzania is missing the denomination.