HKPD depth - EPSG:7976

WKT

VERTCS["HKPD_depth", 
	VDATUM["Hong_Kong_Principal_Datum"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", -1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["HKPD_depth", 
	VDATUM["Hong_Kong_Principal_Datum"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", down, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "7976"]]

Data from @esri/proj-codes

{
  "wkid": 7976,
  "latestWkid": 7976,
  "macro": "PE_VCS_HKPD_D",
  "name": "HKPD_depth",
  "wkt": "VERTCS[\"HKPD_depth\",VDATUM[\"Hong_Kong_Principal_Datum\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",-1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"HKPD_depth\",VDATUM[\"Hong_Kong_Principal_Datum\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",down,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"7976\"]]",
  "description": "HKPD depth",
  "authority": "EPSG",
  "version": "9.2(10.8.0)",
  "deprecated": "no",
  "areaname": "Hong Kong - onshore",
  "extent": {
    "slat": 22.19,
    "nlat": 22.56,
    "llon": 113.82,
    "rlon": 114.39
  }
}