Here is few versions of Jigen ryu bokken, made by original specifications and with my precision,
below is oak bokken by original dimensions, sory (blade curvature) of this bokke is about 5 mm, I make him for my collection because europe oak is not best wood for bokken
below is version with little bigger sory (only on blade part), about 10 mm
and below is one Jigen bokken without sory, made of heavy European oak,