Travis wrote a bit on this not too long ago, but for those of us more visually inclined 9-Hole reviews has a video here on the magnifier trick of using a scope through an RDS or Holographic optic.
As mind breaking as it seems the concept is simple. A magnifier is simply a reticule free scope. Putting a regular fixed scope behind the dot can work the same way as long as the objective lens can gather the light properly from the dot. Neat solution to pre-LPVO mainstream life and times.