Inherited Cartier Pen

Hello, I just graduated high school this past June, and this pen was given to me as a gift from my grandfather, he told me nothing about the pen, but the name Cartier sounded familiar. So, I was wondering if anyone happen to know the model and possible value of this pen. I've noticed most Cartier's are fairly expensive(in excess of $100). As far as how the pen looks and functions, it is a ballpoint, twist to open, both ends of the pen appear to be gold, including the middle piece where the pen can screw off so you can replace the ink. Also, thought mentioning, I tried to find a pen that was exactly the same as the one I have on ebay, trying to find the model and price point, and after an hour of searching, I have not found a single pen that matches mine. Hope to get some good information! Thanks.
-W. Hayden