EH2000 height - EPSG:9663

WKT

VERTCS["EH2000_height", 
	VDATUM["Estonian_Height_System_2000"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["EH2000_height", 
	VDATUM["Estonian_Height_System_2000"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "9663"]]

Data from @esri/proj-codes

{
  "wkid": 9663,
  "latestWkid": 9663,
  "macro": "PE_VCS_EH2000_HEIGHT",
  "name": "EH2000_height",
  "wkt": "VERTCS[\"EH2000_height\",VDATUM[\"Estonian_Height_System_2000\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"EH2000_height\",VDATUM[\"Estonian_Height_System_2000\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"9663\"]]",
  "description": "EH2000 height",
  "authority": "EPSG",
  "version": "10.013(12.8.0)",
  "deprecated": "no",
  "areaname": "Estonia - onshore",
  "extent": {
    "slat": 57.52,
    "nlat": 59.75,
    "llon": 21.74,
    "rlon": 28.2
  }
}