I spoke with Apex directly, and they tell me the L-frame hammer also fits the K-frame.
That's interesting, but it would have to be in one of the later revolvers with a frame mounted firing pin. I know that pre-MIM S&W hammers are different between K and L (and for that matter, N) frames because the distance from the stud hole that the hammer revolves on, to the location of the hammer nose/firing pin is different on all three. I am under the impression that later MIM hammers are also different. Triggers are the same.