I have used the notch a few times, but not something I use much at all. Many people don't understand it well enough to use it, but the disc has to be set less than the notch is set for it to work, the reason is the notch is a variable disc that disc out only a small area that has not been disc out by the main disc. Neither the disc or notch set to max will disc out the zinc pennies or higher, but can disc out the nickles and gold. When I have used mine I set the disc at as low as it will go, or a slight disc, then if there is a certain pull tab or other trash item I don't want to pickup I will swing the coil over that item and turn the notch until I either lose it or the signal breaks up so I know it is not a good target. Now it will not notch out all the trash items, but those that read in that one area I have notched out. Mostly mine when used is the pull tabs like the newer ones that read up in the `160-170 range and found just turn the notch to max and will take care of most of them as they will be broken up signal so I can walk right over them. I still get some of the others that read in the 150, but know they are not good unless the signal is smoother sounding as I will dig those with the hope of a gold ring.
The only time I really use the notch is those areas with a lot of the certain type tabs where you get several in one sweep so I don't have to check each one. It has its purpose when needed.
Rick