The bright circle under the Equitable's builders plate may not be a combination dial...

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there are similar bright circles on the Remote Combination Viewers of these unidentified main and emergency vault doors:

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It looks like the emergency vault door's bright circle has a key hole in it. Could this be a lock to prevent the combination dials from spinning or the to prevent the pressure system hand-wheel from spinning?

These are the only doors I have found with three combination dials on the RCVs.