Vintage 1950s Roller Rule Mechanical Measuring and Math Pencil

Advertised in the 1950s as ‘The Pencil with a Brain’, this is a novelty item in this day and age. 
 
It is primarily a normal lead mechanical or propelling pencil, lead length controlled by turning the top part of the pencil. (Current lead is red for some reason.) 
 
On the far end from the pencil tip, a roller can be used to measure items and distances on maps (using the map scale) by rolling the top with your fingers until the ruler on the body is at 0, then pressing the roller like a tire and rolling it along or next to the item you wish to measure. The white tab on the ruler will move down, measuring in inches, with the top part showing fractions of an inch. 
 
It reportedly can also do math, but we leave that to the buyer to research online.
 
We did not take it apart to find out if there is extra lead or an eraser stored within the body as designed.
 
L 5 7/8” x Diameter 1/2”
 
Disclaimer: We have tried to make sure colors shown in photos are representative of the real colors of each item. We have tried to identify all imperfections in descriptions, but we may have missed some. If you are unhappy with your purchase, let us know.