MONREF 1997 - ESRI:104134

WKT

GEOGCS["GCS_MONREF_1997", 
	DATUM["D_ITRF_2000", 
		SPHEROID["GRS_1980", 6378137.0, 298.257222101]], 
	PRIMEM["Greenwich", 0.0], 
	UNIT["Degree", 0.0174532925199433]]

WKT2

GEOGCRS["GCS_MONREF_1997", 
	DYNAMIC[
		FRAMEEPOCH[1997.0]], 
	DATUM["D_ITRF_2000", 
		ELLIPSOID["GRS_1980", 6378137.0, 298.257222101]], 
	PRIMEM["Greenwich", 0.0], 
	CS[ellipsoidal, 2], 
	AXIS["Longitude (lon)", east, 
		ORDER[1]], 
	AXIS["Latitude (lat)", north, 
		ORDER[2]], 
	ANGLEUNIT["Degree", 0.0174532925199433], 
	ID["Esri", "104134"]]

Data from @esri/proj-codes

{
  "wkid": 104134,
  "latestWkid": 104134,
  "macro": "PE_GCS_MONREF_1997",
  "name": "GCS_MONREF_1997",
  "wkt": "GEOGCS[\"GCS_MONREF_1997\",DATUM[\"D_ITRF_2000\",SPHEROID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]",
  "wkt2": "GEOGCRS[\"GCS_MONREF_1997\",DYNAMIC[FRAMEEPOCH[1997.0]],DATUM[\"D_ITRF_2000\",ELLIPSOID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],CS[ellipsoidal,2],AXIS[\"Longitude (lon)\",east,ORDER[1]],AXIS[\"Latitude (lat)\",north,ORDER[2]],ANGLEUNIT[\"Degree\",0.0174532925199433],ID[\"Esri\",\"104134\"]]",
  "description": "MONREF 1997",
  "authority": "Esri",
  "version": "9.2.0",
  "deprecated": "no",
  "areaname": "Mongolia",
  "extent": {
    "slat": 41.58,
    "nlat": 52.15,
    "llon": 87.76,
    "rlon": 119.94
  },
  "frameEpoch": 1997,
  "deformationModel": ""
}