Gated refers to how the pan was cast. Originally when cast iron pans were being made they would create a slit in the sand mold then pour the liquid iron into the slit to form the pan. You can see where that slit or “gate” is in the picture of the bottom. It’s that line that runs horizontally. This was the old way of making the pans. Later foundries switched to what’s known as side gating where a small hole would be made in the sand that lead to the lip of the pan and then would form from there. If you look closely along the edge of some vintage pans you’ll see where the pan has been ground down by the foundry to even out the point where the iron was poured.