The Monarch RL comes in a large variety of tunes, but what is commonly available in the aftermarket is the M-rebound / M-compression tune.
The 2015 version features the black damper body as well as the "Rapid Recovery" rebound circuit.
"Rapid Recovery" rebound is Rockshox's way of referring to a digressive rebound shim stack. On the Monarch series of shocks this is achieved by preloading the rebound shim stack using a ring shim (as opposed to a dished piston face - the other common method). Most suspension tuning focuses on the compression stack. Tuning the rebound stack is often ignored. The theory behind digressive rebound stacks is sound - at low rebound energies you want more rebound damping for stability, but for high speed events you want fast rebound to allow the suspension to respond quickly between succesive hits and not pack down.
I have used this shock on an Anthem X which normally takes a Monarch with LM tune (low rebound and mid compression). The M rebound tune of this 2015 shock with rapid recovery works surprisingly well. I was expecting the shock to need a revolve to L rebound specs but for e moment I am more than happy with how the M rebound tune is working on my Anthem.
The shock is described as having adjustable rebound and lockout. The lockout is surprisingly effective. It is not a total lockout, but the lockout platform is sufficiently firm that riding with the shock locked out feels nice and efficient.