This is the MSD box with boost timing master ignition box with boost/ retard and rev limiter.
The 6 BTM lets you dial away detonation by retarding the timing in relation to the boost pressure. A dash mounted control knob lets you adjust the amount of timing retard. It can be adjusted from 0 degrees per pound of boost to 3 degrees per pound (up to 15 degrees). The 6 BTM also shares the soft touch rev control of the 6AL ignition for over rev protection. Comes with MSD Blaster High Vibration coil. New this setup is $560.
The box is in excellent condition. Had it upgraded and coil tested from MSD