What is this panel in basement wall of 1940s house?
Would this be in an area that snows or could get cold. It's not a coal chute as most of those were not under the front door. My thinking is this - Warmer air from the cellar escapes and keeps the area in front of the door free from ice and snow -hence the gravel which probably extends down the outside wall. Its a simple convection heat source and very energy efficient.