The pin is recessed and about 1mm in diameter - which seems impossibly small for 6.67A.
Because it doesn't carry 6.67A. What you have there is a laptop power supply, probably an HP or Dell one. The current is carried on the inner and outer sleeve of the barrel. The centre pin only carries communication signals.
But you are correct - there does seem to be a recessed metal inner sleeve. I had looked for one, but couldn't see one - tried again after your post (with a brighter light!)
I still need a chassis mount socket for it, though....
There is a 12v car lead - which makes me wonder if that centre pin is actually used at all...
I guess you could check if it's a physical fit for an HP (or Dell or Samsung) one and then go to ebay or aliexpress and buy a corresponding "laptop charger socket". Though they're all board mount. I don't know if any panel mount ones even exist.
Thanks for the suggestion - I think that there are inline adapters to a different plug, but finding a different coaxial plug that will handle that current could prove challenging.