My vote is for the blacksmith's hammer.   I have a distinct image in my mind of
 the exact hammer you describe.   My father owns a set of 19th century blacksmit
hing tools, and the hammer is there.   It was used to cut iron by striking it wi
th the wedged end. 

Are you sure you strike the iron with the wedged end? I have this vague recollec
tion of watching someone use such a device but the wedge is placed against the i
ron and the other end is struck with another hammer. that would explain why the 
handle isn't very substantial, it wouldn't need to be if it were used in this wa
y.

Dan