EPSG:4009 - Unknown datum based upon the Clarke 1866 Michigan ellipsoid

{
  "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
  "type": "GeographicCRS",
  "name": "Unknown datum based upon the Clarke 1866 Michigan ellipsoid",
  "datum": {
    "type": "GeodeticReferenceFrame",
    "name": "Not specified (based on Clarke 1866 Michigan ellipsoid)",
    "ellipsoid": {
      "name": "Clarke 1866 Michigan",
      "semi_major_axis": {
        "value": 20926631.531,
        "unit": {
          "type": "LinearUnit",
          "name": "US survey foot",
          "conversion_factor": 0.304800609601219
        }
      },
      "semi_minor_axis": {
        "value": 20855688.674,
        "unit": {
          "type": "LinearUnit",
          "name": "US survey foot",
          "conversion_factor": 0.304800609601219
        }
      }
    }
  },
  "coordinate_system": {
    "subtype": "ellipsoidal",
    "axis": [
      {
        "name": "Geodetic latitude",
        "abbreviation": "Lat",
        "direction": "north",
        "unit": "degree"
      },
      {
        "name": "Geodetic longitude",
        "abbreviation": "Lon",
        "direction": "east",
        "unit": "degree"
      }
    ]
  },
  "scope": "Not recommended.",
  "area": "Not specified.",
  "bbox": {
    "south_latitude": -90,
    "west_longitude": -180,
    "north_latitude": 90,
    "east_longitude": 180
  },
  "id": {
    "authority": "EPSG",
    "code": 4009
  }
}

{'crs_wkt': 'GEOGCRS["Unknown datum based upon the Clarke 1866 Michigan '
            'ellipsoid",DATUM["Not specified (based on Clarke 1866 Michigan '
            'ellipsoid)",ELLIPSOID["Clarke 1866 '
            'Michigan",20926631.531,294.978697164677,LENGTHUNIT["US survey '
            'foot",0.304800609601219]]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433]],CS[ellipsoidal,2],AXIS["geodetic '
            'latitude '
            '(Lat)",north,ORDER[1],ANGLEUNIT["degree",0.0174532925199433]],AXIS["geodetic '
            'longitude '
            '(Lon)",east,ORDER[2],ANGLEUNIT["degree",0.0174532925199433]],USAGE[SCOPE["Not '
            'recommended."],AREA["Not '
            'specified."],BBOX[-90,-180,90,180]],ID["EPSG",4009]]',
 'geographic_crs_name': 'Unknown datum based upon the Clarke 1866 Michigan '
                        'ellipsoid',
 'grid_mapping_name': 'latitude_longitude',
 'horizontal_datum_name': 'Not specified (based on Clarke 1866 Michigan '
                          'ellipsoid)',
 'inverse_flattening': 294.97869716467716,
 'longitude_of_prime_meridian': 0.0,
 'prime_meridian_name': 'Greenwich',
 'reference_ellipsoid_name': 'Clarke 1866 Michigan',
 'semi_major_axis': 6378450.047548896,
 'semi_minor_axis': 6356826.621488444}