Work on creating more of the necessary data models

module/models/Item/Equipment.mjs

@@ -0,0 +1,15 @@
+import { DescribedItemData } from "./DescribedItemData.mjs";
+
+export class EquipmentItemData extends DescribedItemData {
+	static defineSchema() {
+		const fields = foundry.data.fields;
+		return mergeObject(super.defineSchema(), {
+			extra_inventory: new fields.NumberField({
+				initial: null,
+				nullable: true,
+				required: false,
+			}),
+			material
+		});
+	};
+};