Unidentified object in gas tank

It looks like a locking gas cap with the chrome top missing.

John

Flux Capacitor!

(Or a broken locking cap)

Government tracking device

(or a broken locking gas cap)

-G

...Locking Gas Cap...they lost the key! Pried the Cap off, and THAT dropped into the Tank! The Locking Tangs are still extended!
OR..Gasoline Theft!...

Three-step, steam driven, middle gas distributor of course

I think it's one of those secret devices the government has been suppressing for the last 40 years that enables a car to get 200 mpg. No doubt some nameless federal agency will show up in the dead of night and 'confiscate' it now that you posted it online! Or, they'll steal gas from your now unlocked gas tank!

Thanks guys, that explains it.