A good core retunr for a factory overhauled Slick Magneto is going to be a current series 4300 or 6300 Slick Magneto. If a new Slick Magneto is purchased, then older series Slick Magnetos can be considered for credit on a case by case basis.
Check the "Detail" tab of the Slick Magneto that you are interested in buying and the Slick Magneto listed with a "Type: Impulsed" will come up with an impulse coupling.
According to the Slick Magneto by Champion Overhaul Manual L-1363F, the magneto should be overhauled at TBO, lighting strike, prop strike, sudden stoppage of the engine and immersion of the aircraft.
Potential Alternates
Please verify product details for suitability for your application.