Gamescience is best known for its old school RPG precision polyhedral dice. But they also released other game campaign support materials like blank poster maps.
Gamescience calls this Fantasy Mapping Grid (1982). I currently (May 2021) have this ziplock set up for auction. There are 6 poster-sized sheets with numbered squares. Printed on both sides.
A set of Gamescience “large hex” mapping paper that came through the shop in 2014.
Here’s a lot of GS hex paper that I cleared out of my boneyard and sold in 2019.
19mm Panzer Size hex paper I sold in 2011.
Lou Zocchi Gamescience order form. Some of the map sheets appear here.