Searching my brain for the two marks you are asking about. If you mean on the side of the key, next to the curve, those are there to make it fit tightly in the crankshaft keyway. In other words, you almost have to hammer it into the keyway. Now what’s this about one way, taper? Maybe I don’t understand your question.

It’s important to remember that the key is simply an alignment tool to correctly place the flywheel in time with the crankshaft and magneto. If the flywheel retaining nut is not torqued to the proper spec, and it’s too loose, the flywheel will float around on the crank and eventually damage the keeways and shear the key. Some of us like to use some Clover brand valve grinding compound on the tapers while rotating the flywheel back and forth to intimately match the tapers. (clean all residue of compound before final assembly) Assemble the flywheel to the crank dry. Use no lubricant between them, and always use a strap wrench and torque wrench. R.T.