LCVD61 height (Intl Feet) - EPSG:6131

WKT

VERTCS["LCVD61_height", 
	VDATUM["Little_Cayman_Vertical_Datum_1961"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Foot", 0.3048]]

WKT2

VERTCRS["LCVD61_height", 
	VDATUM["Little_Cayman_Vertical_Datum_1961"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Foot", 0.3048]], 
	ID["EPSG", "6131"]]

Data from @esri/proj-codes

{
  "wkid": 6131,
  "latestWkid": 6131,
  "macro": "PE_VCS_LCVD61_HT",
  "name": "LCVD61_height",
  "wkt": "VERTCS[\"LCVD61_height\",VDATUM[\"Little_Cayman_Vertical_Datum_1961\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Foot\",0.3048]]",
  "wkt2": "VERTCRS[\"LCVD61_height\",VDATUM[\"Little_Cayman_Vertical_Datum_1961\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Foot\",0.3048]],ID[\"EPSG\",\"6131\"]]",
  "description": "LCVD61 height (Intl Feet)",
  "authority": "EPSG",
  "version": "8.1.2(10.2.1)",
  "deprecated": "no",
  "areaname": "Cayman Islands - Little Cayman",
  "extent": {
    "slat": 19.63,
    "nlat": 19.74,
    "llon": -80.14,
    "rlon": -79.93
  }
}