SA LLD height - EPSG:9279

WKT

VERTCS["SA_LLD_height", 
	VDATUM["South_Africa_Land_Levelling_Datum"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["SA_LLD_height", 
	VDATUM["South_Africa_Land_Levelling_Datum"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "9279"]]

Data from @esri/proj-codes

{
  "wkid": 9279,
  "latestWkid": 9279,
  "macro": "PE_VCS_SA_LLD_HT",
  "name": "SA_LLD_height",
  "wkt": "VERTCS[\"SA_LLD_height\",VDATUM[\"South_Africa_Land_Levelling_Datum\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"SA_LLD_height\",VDATUM[\"South_Africa_Land_Levelling_Datum\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"9279\"]]",
  "description": "SA LLD height",
  "authority": "EPSG",
  "version": "9.8.5(12.6.0)",
  "deprecated": "no",
  "areaname": "South Africa - onshore",
  "extent": {
    "slat": -34.88,
    "nlat": -22.13,
    "llon": 16.45,
    "rlon": 32.95
  }
}