Bat

We can speculate based on the seemingly default values that these bats were the result of an item server glitch or exploit.

The defindex is 0. All TF2 items have a unique index number called the defindex, and for Bats, the defindex is 0.

The quality is 0. All item qualities have a numerical ID, and the ID for Normal quality is 0.

The level is 0. All items in TF2 can have a level from 0-255, and the Normal Bats are all level 0.

The origin is 0. All items in TF2 have a numerical origin ID, and for Normal Bats, it is always 0 (Timed-Drop).

There are '5' Level 0 and '9' Level 1 Normal Bats in existence.

Source