There was some talk recently that all M3Ws have a locking filler cap, but that MMC only have one key number, so your key will open all.
Milligoon came over today (2010 Roadster) so I tried my key (2014 Plus 8) in his lock.
So we compared key numbers.
Exactly the same.
Then we compared door locks. Amazing, they were different!!
It is nice to know that only a fellow Morgan owner can steal your fuel.