G'day all
In fact, it's a pretty basic idea harking back to the toe cutters.
It's a edging port - to get the blade tips close to walls.
Note how it is on the LH side (with blade tips moving forward).
The RH side has a discharge port, making this a true side and rear
discharge lawnmower (to be used as desired).

[Linked Image]

Both Victa and Pope had edging ports on some models.
After 1968 they were considered not safe.

Cheers
---------------
Jack