Hi Pancake,
I also believe the most popular collectable would be all 3 series of the Model 5.
You will see Pancake that Blumbly refers to
all 3 series of the Model 5....the first Model 5 has the extensions for the Predicta flap set up and 4 side skirt holes (left over from the Model 4 Automatic) and the edger slot; the second had the edger slot only and 2 side skirt holes; and the third model had the edger slot and holes deleted all together.