St Kilda - EPSG:5747

WKT

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

WKT2

VERTCRS["St_Kilda", 
	VDATUM["St_Kilda"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "5747"]]

Data from @esri/proj-codes

{
  "wkid": 5747,
  "latestWkid": 5747,
  "macro": "PE_VCS_ST_KILDA",
  "name": "St_Kilda",
  "wkt": "VERTCS[\"St_Kilda\",VDATUM[\"St_Kilda\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"St_Kilda\",VDATUM[\"St_Kilda\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"5747\"]]",
  "description": "St Kilda",
  "authority": "EPSG",
  "version": "6.15(9.3.0.0)",
  "deprecated": "no",
  "areaname": "UK - St. Kilda onshore",
  "extent": {
    "slat": 57.74,
    "nlat": 57.93,
    "llon": -8.74,
    "rlon": -8.41
  }
}