What ate the fuel sender float?

[sick472]

I've only pulled a few fuel sending units in my life, all pre-72 and all brass floats, but I've never seen one like this. It looks like brass. The edges of the hole are very thin and would be sharp if it was not so thin.

I've had the truck since 1995 and drove it for a few years back then. The fuel gauge worked then, but since then the tank has had 87 octane in it mostly setting in the garage waiting "for the day".

Needless to say, it's getting replaced and the tank will get cleaned out an maybe epoxied (it's speckled with light rust). While were talking sending units....Any suggestions as who sells the good stuff?

BUT, What happened here?...