Stuffed Olives© Denzil Green
Olives used to be stuffed by hand, but now it is almost always done by machine.
Machines first pit the olives, then stuff the cavity they made with a filling. The stuffing can be almonds, anchovy, celery, onion or strips of pimiento paste. New stuffings being thought of all the time.
The size of the stuffing has to match exactly the size of the hole that the pitting machine has punched: if the strip is too narrow, the stuffing will fall out of the larger hole; if the strip is too wide for the hole, it could crack the olive making it a broken olive which sells for less.
Commercial Stuffed Olives are always green, as Black Olives are too soft to survive the pitting process.