Using efarlow's as a starting point, I modeled mine to match the key off a Harbor Freight table saw. The actual useful, two-prong key part has identical dimensions.
I printed the key as it is normally oriented, and I used line-type supports in Cura for the two prongs. If you rotate and print on its face, you'll find those little prongs don't come out as nice and, because of the plastic "grain", are very fragile (at least using PLA).
Hatchbox Gold PLA @ 200 degrees