SLD99 - ESRI:115793

WKT

VERTCS["SLD99", 
	DATUM["D_Sri_Lanka_Datum_1999", 
		SPHEROID["Everest_Adjustment_1937", 6377276.345, 300.8017]], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["SLD99", 
	DATUM["D_Sri_Lanka_Datum_1999", 
		ELLIPSOID["Everest_Adjustment_1937", 6377276.345, 300.8017]], 
	CS[vertical, 1], 
	AXIS["Ellipsoidal height (h)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["Esri", "115793"]]

Data from @esri/proj-codes

{
  "wkid": 115793,
  "latestWkid": 115793,
  "macro": "PE_VCS_SLD99",
  "name": "SLD99",
  "wkt": "VERTCS[\"SLD99\",DATUM[\"D_Sri_Lanka_Datum_1999\",SPHEROID[\"Everest_Adjustment_1937\",6377276.345,300.8017]],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"SLD99\",DATUM[\"D_Sri_Lanka_Datum_1999\",ELLIPSOID[\"Everest_Adjustment_1937\",6377276.345,300.8017]],CS[vertical,1],AXIS[\"Ellipsoidal height (h)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"Esri\",\"115793\"]]",
  "description": "SLD99",
  "authority": "Esri",
  "version": "10.4.0",
  "deprecated": "no",
  "areaname": "Sri Lanka - onshore",
  "extent": {
    "slat": 5.86,
    "nlat": 9.88,
    "llon": 79.64,
    "rlon": 81.95
  }
}