Bluff - EPSG:5760

WKT

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

WKT2

VERTCRS["Bluff", 
	VDATUM["Bluff"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "5760"]]

Data from @esri/proj-codes

{
  "wkid": 5760,
  "latestWkid": 5760,
  "macro": "PE_VCS_BLUFF",
  "name": "Bluff",
  "wkt": "VERTCS[\"Bluff\",VDATUM[\"Bluff\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"Bluff\",VDATUM[\"Bluff\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"5760\"]]",
  "description": "Bluff",
  "authority": "EPSG",
  "version": "6.15(9.3.0.0)",
  "deprecated": "no",
  "areaname": "New Zealand - South Island - Bluff vcrs",
  "extent": {
    "slat": -46.71,
    "nlat": -46.26,
    "llon": 168.01,
    "rlon": 168.86
  }
}