RGNC 1991 - ESRI:115781

WKT

VERTCS["RGNC_1991", 
	DATUM["D_RGNC_1991", 
		SPHEROID["International_1924", 6378388.0, 297.0]], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["RGNC_1991", 
	DATUM["D_RGNC_1991", 
		ELLIPSOID["International_1924", 6378388.0, 297.0]], 
	CS[vertical, 1], 
	AXIS["Ellipsoidal height (h)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["Esri", "115781"]]

Data from @esri/proj-codes

{
  "wkid": 115781,
  "latestWkid": 115781,
  "macro": "PE_VCS_RGNC_1991",
  "name": "RGNC_1991",
  "wkt": "VERTCS[\"RGNC_1991\",DATUM[\"D_RGNC_1991\",SPHEROID[\"International_1924\",6378388.0,297.0]],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"RGNC_1991\",DATUM[\"D_RGNC_1991\",ELLIPSOID[\"International_1924\",6378388.0,297.0]],CS[vertical,1],AXIS[\"Ellipsoidal height (h)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"Esri\",\"115781\"]]",
  "description": "RGNC 1991",
  "authority": "Esri",
  "version": "10.4.0",
  "deprecated": "no",
  "areaname": "New Caledonia",
  "extent": {
    "slat": -26.45,
    "nlat": -14.83,
    "llon": 156.25,
    "rlon": 174.28
  }
}