Deutz ( industrial diesel ) uses a keyless crank timing belt sprocket on the oil cooled engines. These engines look like a water cooled engine except oil is pumped through the "water jackets"

I think the Toyota V8 does this also.

Other engines do the keyless thing on the cams.

The keykess pulley is used to get valve timing exactly right and not having to worry about a build up of tolerances. It also simplifies assembly, lock the cam and crank into position, throw the timing components at the engine, tighten the bolts.