The slotted lugs permit the gap to be adjusted for different sizes of magnets. And they can be replaced with specially shaped ones to fit oddly shaped magnets. This thing should develop about 25,000 ampere-turns.
Built from the detailed instructions in David Gingery's How to Build a Magneto Magnetizer .
There are also some pics of the winder I rigged up to make the coils.
And a tip of the hat to the guys at L&B Electric in Bridgewater, Nova Scotia for their indispensable help with the project. Thanks, guys!