I buy in bulk like Patrice...if you are questioning if a needle is the same as another...lay the needle from your Pfaff down on a dark table top. Place a Singer needle next to it and examine the lenght of the shaft, the position of the eye, etc. If all is the same...than use it.
You may be thinking about the difference between home needles and industrial sewing machine needles...Industrial needles do not have a flat side on the shaft, they are round. Only home machine needles have a flat side.
The old singer #319's took an industrial needle.