This is a really neat period correct accessory for all those who got tired of having the expensive fog lights or driving lights stolen off their car when parked. Most anyone with expensive wheels on their car should recognize this as a tamper resistant keyed locking nut. The conical piece on left is the female threaded nut to secure the lamp on the bumper. The hex piece on the right is the matching keyed locking driver socket (do not lose your key).

The conical nut has internal keying drilled or milled indents. The hex drive key has matching external pegs. Only your key will fit the nut on your fog lights. You better believe this security nut and key would cost less then a replacement lamp.