Horta height - EPSG:6181

WKT

VERTCS["Horta_height", 
	VDATUM["Horta"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["Horta_height", 
	VDATUM["Horta"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "6181"]]

Data from @esri/proj-codes

{
  "wkid": 6181,
  "latestWkid": 6181,
  "macro": "PE_VCS_HORTA_HT",
  "name": "Horta_height",
  "wkt": "VERTCS[\"Horta_height\",VDATUM[\"Horta\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"Horta_height\",VDATUM[\"Horta\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"6181\"]]",
  "description": "Horta height",
  "authority": "EPSG",
  "version": "8.2(10.2.1)",
  "deprecated": "no",
  "areaname": "Portugal - Azores C - Faial onshore",
  "extent": {
    "slat": 38.46,
    "nlat": 38.7,
    "llon": -28.9,
    "rlon": -28.54
  }
}