Belge Lambert 1950 - EPSG:21500

WKT

PROJCS["Belge_Lambert_1950", 
	GEOGCS["GCS_Belge_1950_Brussels", 
		DATUM["D_Belge_1950", 
			SPHEROID["International_1924", 6378388.0, 297.0]], 
		PRIMEM["Brussels", 4.367975], 
		UNIT["Degree", 0.0174532925199433]], 
	PROJECTION["Lambert_Conformal_Conic"], 
	PARAMETER["False_Easting", 150000.0], 
	PARAMETER["False_Northing", 5400000.0], 
	PARAMETER["Central_Meridian", 0.0], 
	PARAMETER["Standard_Parallel_1", 49.83333333333334], 
	PARAMETER["Standard_Parallel_2", 51.16666666666666], 
	PARAMETER["Latitude_Of_Origin", 90.0], 
	UNIT["Meter", 1.0]]

WKT2

PROJCRS["Belge_Lambert_1950", 
	BASEGEOGCRS["GCS_Belge_1950_Brussels", 
		DATUM["D_Belge_1950", 
			ELLIPSOID["International_1924", 6378388.0, 297.0]], 
		PRIMEM["Brussels", 4.367975, 
			ANGLEUNIT["Degree", 0.0174532925199433]], 
		CS[ellipsoidal, 2], 
		AXIS["Latitude (lat)", north, 
			ORDER[1]], 
		AXIS["Longitude (lon)", east, 
			ORDER[2]], 
		ANGLEUNIT["Degree", 0.0174532925199433]], 
	CONVERSION["Lambert_Conformal_Conic", 
		METHOD["Lambert_Conformal_Conic"], 
		PARAMETER["False_Easting", 150000.0], 
		PARAMETER["False_Northing", 5400000.0], 
		PARAMETER["Central_Meridian", 0.0], 
		PARAMETER["Standard_Parallel_1", 49.83333333333334], 
		PARAMETER["Standard_Parallel_2", 51.16666666666666], 
		PARAMETER["Latitude_Of_Origin", 90.0]], 
	CS[Cartesian, 2], 
	AXIS["Easting (X)", east, 
		ORDER[1]], 
	AXIS["Northing (Y)", north, 
		ORDER[2]], 
	LENGTHUNIT["Meter", 1.0], 
	ID["EPSG", "21500"]]

Data from @esri/proj-codes

{
  "wkid": 21500,
  "latestWkid": 21500,
  "gcsWkid": 4809,
  "macro": "PE_PCS_BELGE_LAMBERT_1950",
  "name": "Belge_Lambert_1950",
  "wkt": "PROJCS[\"Belge_Lambert_1950\",GEOGCS[\"GCS_Belge_1950_Brussels\",DATUM[\"D_Belge_1950\",SPHEROID[\"International_1924\",6378388.0,297.0]],PRIMEM[\"Brussels\",4.367975],UNIT[\"Degree\",0.0174532925199433]],PROJECTION[\"Lambert_Conformal_Conic\"],PARAMETER[\"False_Easting\",150000.0],PARAMETER[\"False_Northing\",5400000.0],PARAMETER[\"Central_Meridian\",0.0],PARAMETER[\"Standard_Parallel_1\",49.83333333333334],PARAMETER[\"Standard_Parallel_2\",51.16666666666666],PARAMETER[\"Latitude_Of_Origin\",90.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "PROJCRS[\"Belge_Lambert_1950\",BASEGEOGCRS[\"GCS_Belge_1950_Brussels\",DATUM[\"D_Belge_1950\",ELLIPSOID[\"International_1924\",6378388.0,297.0]],PRIMEM[\"Brussels\",4.367975,ANGLEUNIT[\"Degree\",0.0174532925199433]],CS[ellipsoidal,2],AXIS[\"Latitude (lat)\",north,ORDER[1]],AXIS[\"Longitude (lon)\",east,ORDER[2]],ANGLEUNIT[\"Degree\",0.0174532925199433]],CONVERSION[\"Lambert_Conformal_Conic\",METHOD[\"Lambert_Conformal_Conic\"],PARAMETER[\"False_Easting\",150000.0],PARAMETER[\"False_Northing\",5400000.0],PARAMETER[\"Central_Meridian\",0.0],PARAMETER[\"Standard_Parallel_1\",49.83333333333334],PARAMETER[\"Standard_Parallel_2\",51.16666666666666],PARAMETER[\"Latitude_Of_Origin\",90.0]],CS[Cartesian,2],AXIS[\"Easting (X)\",east,ORDER[1]],AXIS[\"Northing (Y)\",north,ORDER[2]],LENGTHUNIT[\"Meter\",1.0],ID[\"EPSG\",\"21500\"]]",
  "description": "Belge Lambert 1950",
  "authority": "EPSG",
  "version": "3.1(3.0.1)",
  "deprecated": "no",
  "areaname": "Belgium - onshore",
  "extent": {
    "slat": 49.5,
    "nlat": 51.51,
    "llon": 2.5,
    "rlon": 6.4
  }
}