Militar-Geographische Institut - ESRI:115921

WKT

VERTCS["MGI", 
	DATUM["D_MGI", 
		SPHEROID["Bessel_1841", 6377397.155, 299.1528128]], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["MGI", 
	DATUM["D_MGI", 
		ELLIPSOID["Bessel_1841", 6377397.155, 299.1528128]], 
	CS[vertical, 1], 
	AXIS["Ellipsoidal height (h)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["Esri", "115921"]]

Data from @esri/proj-codes

{
  "wkid": 115921,
  "latestWkid": 115921,
  "macro": "PE_VCS_MGI",
  "name": "MGI",
  "wkt": "VERTCS[\"MGI\",DATUM[\"D_MGI\",SPHEROID[\"Bessel_1841\",6377397.155,299.1528128]],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"MGI\",DATUM[\"D_MGI\",ELLIPSOID[\"Bessel_1841\",6377397.155,299.1528128]],CS[vertical,1],AXIS[\"Ellipsoidal height (h)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"Esri\",\"115921\"]]",
  "description": "Militar-Geographische Institut",
  "authority": "Esri",
  "version": "13.2.0",
  "deprecated": "no",
  "areaname": "Europe - Austria and former Yugoslavia onshore",
  "extent": {
    "slat": 40.85,
    "nlat": 49.02,
    "llon": 9.53,
    "rlon": 23.04
  }
}