Complex sentence: Stamps of the Cape Colony were also overprinted, with "ORANGE RIVER COLONY" (August 10, before the colony officially existed), and only in 1903 did the Orange River Colony get its own stamps.
Split into simpler sentences: Stamps of the Cape Colony were also overprinted, with "ORANGE RIVER COLONY" (August 10, before the colony officially existed). Only in 1903 did the Orange River Colony get its own stamps.