From what I've been told, the 4240 came out at the same time as the Super series of tractors. That was 1954.
The first 4240's had a small tail wheel, and sometime in 1956 they went to the large tail wheel. The 4240 plow was built well into the 60's, and it was the last 2/3 bottom pull type plow that Oliver built. The colors and decal schemes changed with the tractor color/decal/scheme changes. 

I can't help you with the serial number. Somewhere out there somebody may have a list.