Is there supposed to be a plate on the dash behind the key assembly on my 1952 TO-30?
Yes, there should be a switch plate under the nut on the face of the switch. That plate designates the 4 switch positions,
O For Off
I For Ignition
IL For Ignition and Lights
L For Lights
These plates are currently not available, but I do have some New Old Stock ones I can sell. If you are interested, let me know. The plate is similar to the one used on the TO-35, F-40 and later MF tractors, but the shape of the TO-30 plate is different. It is cut to fit the raised section of the dash where the switch is mounted.