While I’m not generally too concerned with pencils, this company would not really exist without them, and it’s worth a quick glance at them.
The inital output, inspired by Charles Keeran’s patent, were not vastly different on the outside from the run of pencils that had appeared even in the late 1800s– rather reminiscent of a nail. While I’m not interested enough in them to examine the patent itself to find if this is the source of the innovation, the clever thing about the early Eversharps is that it was possible to check on how much lead remained in the mechanism without actually extending it completely. Pulling up on the crown of the pen drew out part of the mechanism, but how much depends upon how far the lead’s driver was advanced. The distance between the top of the barrel and the bottom of the crown shows exactly the length of lead remaining.
A less clever aspect of this mechanism is that it could only run one way. Unlike some of the other pencils of the time, the lead was not captive in the mechanism, and the driver was just a simple rod, so the lead could not withdraw once run out. In this, they are similar to wooden pencils, and as lead doesn’t leak, it’s not a huge problem, but it was something that Wahl felt driven to eventually do something about. Reloading these pencils took a fair degree of dismantling, too. Again, it wasn’t a great big deal, given how long a pencil lead lasts relative to a sac-full of ink, but it was a point of inconvenience the competition could make hay of.
If you are relying on the preceding information to win a bet or impress a teacher, you should read the site’s scholarly caveat. Remember, this is the internet, and it’s full of bad information.