In this link to a memorandum on the Cape Law Society website, a number of steps are laid down and discussed for the attorney to follow in the registration of such bonds. The proviso being that it is impossible to lay down a hard and fast rule, as the circumstances will differ with each transaction.
For example, an attorney might know the management, officials or members of a Company or Close Corporation so that he/she could dispense with all evidence of the signatories having the necessary binding authority. In other circumstances, for instance where the attorney has doubts about the ostensible capacity of the signatories, he/she could only be proved to have acted with the reasonable amount of care expected, if he/she had taken the fullest steps in getting the necessary physical evidence about the relevant Company or Close Corporation.
Link to the memorandum