Ratskinner
Adventurer
For me square grids is OSR. I met them the first time I played (AD&D1).That said, my mostly proud OSR group seems stuck on 3.5-like square grids.
2cm (or was it 2.5cm? can't recall) grid paper mounted on a board with a plastic cover, drawn with water soluble OH pens.
Basically the same as I use today.
I never did grids until 3.0. My AD&D groups all did ToTM or analog measurement for combat. Hexes were for overland maps, and grids were something the DM and maybe the party mapper saw. Of course, we might not have been as dungeons as other groups.