Hi Colin, as always thanks for the comments.
From period accounts of travelers in Nigeria it would seem there was no problem to use recycled steel sources, two man saws have been around for a while and I guess would have been a likely trade item even in the early colonial days and 19th century. The blade on this is 8.25cm (over 3 inches) wide at the base. The hole I think was probably filled with a copper slug at one point - I've seen this on some other ultra wide bladed takouba.