I got this at a stall at the Kalk Bay Market last weekend, dating from the days of the Union of South Africa.
I thought it was a date stamp, as there are 6 wheels with numbers.
But upon trying it out I realized that it was used to number copies of documents.
Wheeeeee! I can number something up to 999999! (Perhaps the number of pages I am still waiting for from the two publishers? Both late, and with only four days to finish them ...)