It's not pre-Anniversary, it's the Anniversary model made between 1940 & 47.
So be careful when looking for parts, nothing is common between the pre-Anniversary & Pacemaker models, I have rebuilt both. However some parts from the Anniversary are similar to the pre-Anniversary and others the Pacemaker. The back is similar to the pre-Anniversary, the focussing track is newer and like the Pacemakers, but the lens standard is only slightly modified.
My bellows were held in place by two metalbars which unscrewed, on the Pacemaker. I didn't need to remove them on the pre-Anniversary model.
Ian