This is potentially very useful when folding up trays and boxes.
The massive 75 mm square punch is foot driven and arranged by having the cutting face tilted, so that a progressive cut is made. First contact is at the rear, with the shear action progressing forwards to the corner, then from left to right across the other face of the corner.
Now the punch was pretty blunt and someone looked to have titivated it with an angle grinder

However I brought it down parallel to what looks to be the original face giving clean cutting edges. As the face tilts in two directions but is a plane, it was a tricky bit of setting up.
It now cuts very happily on its first fore & aft edge, but with the 1.5 mm plate I've been using it is virtually impossible to progress the cut on the side to side direction.
Now if you look at the two sides of the cutter block, they have markedly differing angles to them.