Slightly Damaged Anvils and Very Damaged Anvils don't display the correct texture when falling.
Steps to reproduce:
1. Place a damaged anvil on a block suspended in the air.
2. Break the block underneath the anvil so it falls.
The texture will be different.
Environment
Mac OS X, latest stable release of Java
It works like sand. When it drops, the falling item has only one texture.
Yes, it is a bug. They should make appropriate textures for each one.