One of the disadvantages of using numismatics for the study of African history is that it is not entirely reliable. The simple reason is that the numismatists are, after all, human and therefore prone to distortions and not getting it entirely right. It is possible for them to arrive at the wrong conclusions.
The original purpose of the convention was to search for ways to improve the Articles of Confederation. However the Framers changed the purpose to writing a new constitution because they thought the problems were too serious to try correct.