Upon issuance of the 1901 Yacht Issues, an unknown number of copies were overprinted and distributed to post offices as specimens.
Upon the issuance of the 1905 / 1919 watermarked Yacht Issues, imperforate sheets were printed of several of the values for the archive of the Reichsdruckerei (Reich Printing Works).
Proof printings of the 20-, 45-, and 60 Heller values of the unwatermarked Yacht Issues were printed in several trial colors.
Prior to printing of the first Yacht Issues, a proof was produced of the 2 Pesa issue.
Proof printings of the 2- & 3 Rupien values were printed in trial colors that vary from the colors of the eventual issues.
Upon occupying Mafia Island, the British used a handstamp to overprint German East Africa issues for use by British forces in the area. The first issues were overprinted ‘G. R. / MAFIA’, and they can be found with black or blackish-violet ink.