Helmert 1906 - EPSG:4020

WKT

GEOGCS["GCS_Helmert_1906", 
	DATUM["D_Helmert_1906", 
		SPHEROID["Helmert_1906", 6378200.0, 298.3]], 
	PRIMEM["Greenwich", 0.0], 
	UNIT["Degree", 0.0174532925199433]]

WKT2

GEOGCRS["GCS_Helmert_1906", 
	DATUM["D_Helmert_1906", 
		ELLIPSOID["Helmert_1906", 6378200.0, 298.3]], 
	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", "4020"]]

Data from @esri/proj-codes

{
  "wkid": 4020,
  "latestWkid": 4020,
  "macro": "PE_GCS_HELMERT_1906",
  "name": "GCS_Helmert_1906",
  "wkt": "GEOGCS[\"GCS_Helmert_1906\",DATUM[\"D_Helmert_1906\",SPHEROID[\"Helmert_1906\",6378200.0,298.3]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]",
  "wkt2": "GEOGCRS[\"GCS_Helmert_1906\",DATUM[\"D_Helmert_1906\",ELLIPSOID[\"Helmert_1906\",6378200.0,298.3]],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\",\"4020\"]]",
  "description": "Helmert 1906",
  "authority": "EPSG",
  "version": "3.0(3.0.1)",
  "deprecated": "no",
  "areaname": "Not specified",
  "extent": {
    "slat": -90,
    "nlat": 90,
    "llon": -180,
    "rlon": 180
  }
}