Looking again at Don's post I see that all he said is that it was a
"curved" bow.  So I really have no way of knowing whether the bow used is
the contraption that I described in my last post.  The others are correct
to point out that early bows were curved outward; however this was not
designed to make double stopping easier, because there was insufficient
curvature to enable the necessary bending of the hair.  The concave bow
design won out because only it could perform the new bowing techniques that
were developing in the late 18th century--those that demanded a lot of
elasticity of the stick.  The only way Don could tell if the "Bach bow"
were used is if its' specifically mentioned and described in the booklet.

Chris Bonds