Its just a laptop style lock. Look up kensington, they make all sorts of them. They are similar to bike locks, just for electronics.
It's a Kensington lock slot. Used to lock the console up, typically with a light duty cable looped through a piece of furniture and then a lock that secures in the slot.
It's a Kensington lock... It's basically so you can chain it down if you want to... Can't post pictures on this forum any more, but I did way back.
Try a search using Kensington on this forum or Google.
And if anyone wants to buy one I have about ten of them from when Comet closed, haha.