Anyone know what this thing is?

[postmortem]

I just purchased an MK4 arcade and on the bezzel there is thist weird red circle. It doesnt seem to light up. Does anyone know what it is and what its used for?

[JcProAm]

if i remember correctly that is what turns the time circuits on.  Just make sure you have enough plutonium for the return trip.     Does it look like it is aftermarket or added on?

[Kevin Mullins]

Have you looked inside the cabinet to see what it's connected to?

[CrazyKongFan]

It''s the history eraser button!

[Spacejack]

Looks like an infra-red eye to me.  don;t know what it would be for, unless there's a remote...

[Hoopz]

Skynet.

[mytymaus007]

Its a warning light When it turns on it means your wife or girlfriend just came home and you'll have to help bring in the packages

[Thenasty]

thats device is to hypnotize the player so that they keep shoving/feeding the machine money. 

[postmortem]

I just got it. I havent opened it up to check what its connected to yet. I will tonight and let ya know

[Necro]

It's a nipple.  It's how the cab feeds baby cabs before they are ready to forage for quarters on their own.

[SammyWI]

It's the HAL 9000 unit.  Remember, he can read lips.

[postmortem]

love the responses 
i took off the glass and found that its just a piece of plastic.. nothing is connected to it. I wonder why someone would drill a hole in the bezel to add this red plastic thing. maybe it was part of some arcade's security systems.