LUREF - EPSG:4181

WKT

GEOGCS["GCS_LUREF", 
	DATUM["D_Luxembourg_Reference_Frame", 
		SPHEROID["International_1924", 6378388.0, 297.0]], 
	PRIMEM["Greenwich", 0.0], 
	UNIT["Degree", 0.0174532925199433]]

WKT2

GEOGCRS["GCS_LUREF", 
	DATUM["D_Luxembourg_Reference_Frame", 
		ELLIPSOID["International_1924", 6378388.0, 297.0]], 
	PRIMEM["Greenwich", 0.0], 
	CS[ellipsoidal, 2], 
	AXIS["Latitude (lat)", north, 
		ORDER[1]], 
	AXIS["Longitude (lon)", east, 
		ORDER[2]], 
	ANGLEUNIT["Degree", 0.0174532925199433], 
	ID["EPSG", "4181"]]

Data from @esri/proj-codes

{
  "wkid": 4181,
  "latestWkid": 4181,
  "macro": "PE_GCS_LUREF",
  "name": "GCS_LUREF",
  "wkt": "GEOGCS[\"GCS_LUREF\",DATUM[\"D_Luxembourg_Reference_Frame\",SPHEROID[\"International_1924\",6378388.0,297.0]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]",
  "wkt2": "GEOGCRS[\"GCS_LUREF\",DATUM[\"D_Luxembourg_Reference_Frame\",ELLIPSOID[\"International_1924\",6378388.0,297.0]],PRIMEM[\"Greenwich\",0.0],CS[ellipsoidal,2],AXIS[\"Latitude (lat)\",north,ORDER[1]],AXIS[\"Longitude (lon)\",east,ORDER[2]],ANGLEUNIT[\"Degree\",0.0174532925199433],ID[\"EPSG\",\"4181\"]]",
  "description": "LUREF",
  "authority": "EPSG",
  "version": "6.5(9.0.0)",
  "deprecated": "no",
  "areaname": "Luxembourg",
  "extent": {
    "slat": 49.44,
    "nlat": 50.19,
    "llon": 5.73,
    "rlon": 6.53
  }
}