The E-6B is actually the back side of the computer. That is a graphic representation of the wind triangles and does a very good job of helping the pilot to understand what the wind does. The front side was originally called the Dalton Ded-Reckoning Computer. It is a circular slide rule and involves all of the estimation skills of a regular slide rule. Besides, if Mr. Spock in Star Trek TOS is using one in the 23d century, it must have some value.