To start with, the envelope and letter are high quality Stationary.
The Tooth Fairy starts the letter with your child's first name.
Your child's home state will be mentioned.
Next, the letter is signed by the Tooth Fairy using a real pen, not a computer generated signature.
The envelope will be addressed personally to your child.
A brother, sister, grandparent, or best friend's name will be mentioned. This will make the letter really believable.