If you look at the "Rock chips on hood" image, you can see 2 holes drilled on one side of the top of the bumper. I'm guessing there were driving or fog lights mounted there at one time and that switch was for those lights.
The other possibility is that the switch is (or was) part of the Gulf States Toyota alarm system. They used a different alarm than the Toyota USA alarms. You'll notice it has a red LED that seems to be part of an alarm system but that might be original.
that on off switch is deff a light switch i have 4 of them in my cruiser right now. i got them from spector off road back when i had my first 40 and installed lights using there switch and wire kit. the switches pop right into factory cut out in an 80.
Im not against factory lockers in anyway. That said short of a detroit, nothing is stronger than an ARB! Yes you have to deal with air lines, so what. Just route them correctly. I guess my point is that dont not buy an 80 just because you cant find one with factory lockers. You can always put in ARB's and be very well off. I dont have factory electric experience personally, but Ive built 5 rigs with dual ARB's and Im friends with the ARB guys in Seattle.
I have the factory lockers on my 97' FZJ and they have been very tempermental for a long time. I may sell the axles and get ARBs in the future when the FZJ will get to see a lot of trails, that is how impressed I am with them. I am sure they are strong and all, but having to wait for them to lock when they are being tempermental may be counterproductive in a situation that I really need them. I have been with my friends who have "other" 4x4s and the ARBs locked/unlocked very quickly. I can just imagine a situation where I need the lockers and all I get is the blinking dash light My 01' Tacoma has the same type of locker and it was never as quick to engage and disengage as the ARB. If installed properly the ARBs are the better choice. For those of you with OEM lockers I am sure if they are working %100 they are great. Isn't there something about the splines twisting and getting stuck making a trail fix nearly impossible? (but I think you need to have tires taller than 36s for this to be a concern) Anyways, my 0.02$.
I've had experienced with both and have to agree my favoriate things about having arbs is the speed in which they engage. With the exception of having blowen a fuse on my compressor, everything else with my ARB has worked flawlesly.