Hi, mega twin,
You are describing a gun with a transfer bar. Your procedure won't work on an S&W revolver because the rebound slide will retract the hammer with or without the hammer block. The hammer block is intended for a real disaster where the hammer is hit so hard it crushes the rebound slide or the hammer pin shears off.
If DG45 looks into the frame in front of the hammer and can't see a hammer block moving sideways as the gun is cocked, then there isn't any. He should also be able to see the slot in the sideplate from there without taking the sideplate off.