In my post on the 30, I included a picture of it next to what was then the newest model I owned, the Guardian C154B. Since acquiring the C154E, it seems appropriate to feature the oldest and the newest together. Actually, I happen to be using the C154E as my upstairs machine right now, and I thought I'd also take out the 30 for a little light work (I do like using my older vacuums, but I'd never over-use them).
Its fascinating to note that there is approximately 70 years in the difference between these two models, and yet the basic design is the same. The only real noticeable change over the years is the location of the power cord and the direction of the exhaust (from the rear end to the top). When something works, it doesn't need much fixing.
