The Burger Senate Wax seal was used to denote Free Postage during the Batavian Republic period of the Cape of Good Hope, when after the Treaty of Amiens the first British Occupation was terminated and the Cape of Good Hope was restored to the Batavian Republic.
No other handstamps were used during the Batavian Republic period. The only one known is from the Burgher Senate illustrated here. This was actually a wax seal but is known to have been used to mark free postage.(See the image below shown the Burgher Senate seal).
The Burgher Senate Seal can be found impressed on wax. As this was the normal use for this handstamp it explains the poor nature of impressions on letters. Only three or four known copies of this datestamp exist.