def estimate_sheet_type(sheet):
    """Estimate sheet type based on sheet name."""
    sheet = sheet.lower()
    if "coord" in sheet:
        return "Coordinates"
    if "loc" in sheet:
        return "Locations"
    if "item" in sheet:
        return "Items"
    if "inv" in sheet:
        return "Inventory"
    if "ord" in sheet:
        return "Orders"
    return "None"