Hi there
If it is a Howard Bantam then the mower unit bolts on in place of the rotor box, the mower actually sticks out in an offset position to one side. They cut very well, the only problem I found is that if the mower encountered a bump in the ground or some other obstruction, the machine was nearly wrenched out of your hands as it wanted to swerve to the right violently.
They are not very plentiful now and the grassboxes are even more rare.