DHHN85 - EPSG:5784

WKT

VERTCS["DHHN85", 
	VDATUM["Deutsches_Haupthoehennetz_1985"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["DHHN85", 
	VDATUM["Deutsches_Haupthoehennetz_1985"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "5784"]]

Data from @esri/proj-codes

{
  "wkid": 5784,
  "latestWkid": 5784,
  "macro": "PE_VCS_DHHN85",
  "name": "DHHN85",
  "wkt": "VERTCS[\"DHHN85\",VDATUM[\"Deutsches_Haupthoehennetz_1985\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"DHHN85\",VDATUM[\"Deutsches_Haupthoehennetz_1985\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"5784\"]]",
  "description": "DHHN85",
  "authority": "EPSG",
  "version": "6.7(9.3.0.0)",
  "deprecated": "no",
  "areaname": "Germany - West Germany all states",
  "extent": {
    "slat": 47.27,
    "nlat": 55.09,
    "llon": 5.86,
    "rlon": 13.84
  }
}