EOS21-IRF - EPSG:9739

WKT

GEOGCS["EOS21-IRF", 
	DATUM["EOS21_Intermediate_Reference_Frame", 
		SPHEROID["GRS_1980", 6378137.0, 298.257222101]], 
	PRIMEM["Greenwich", 0.0], 
	UNIT["Degree", 0.0174532925199433]]

WKT2

GEOGCRS["EOS21-IRF", 
	DATUM["EOS21_Intermediate_Reference_Frame", 
		ELLIPSOID["GRS_1980", 6378137.0, 298.257222101]], 
	PRIMEM["Greenwich", 0.0], 
	CS[ellipsoidal, 2], 
	AXIS["Latitude (lat)", north, 
		ORDER[1]], 
	AXIS["Longitude (lon)", east, 
		ORDER[2]], 
	ANGLEUNIT["Degree", 0.0174532925199433], 
	ID["EPSG", "9739"]]

Data from @esri/proj-codes

{
  "wkid": 9739,
  "latestWkid": 9739,
  "macro": "PE_GCS_EOS21_IRF",
  "name": "EOS21-IRF",
  "wkt": "GEOGCS[\"EOS21-IRF\",DATUM[\"EOS21_Intermediate_Reference_Frame\",SPHEROID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]",
  "wkt2": "GEOGCRS[\"EOS21-IRF\",DATUM[\"EOS21_Intermediate_Reference_Frame\",ELLIPSOID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],CS[ellipsoidal,2],AXIS[\"Latitude (lat)\",north,ORDER[1]],AXIS[\"Longitude (lon)\",east,ORDER[2]],ANGLEUNIT[\"Degree\",0.0174532925199433],ID[\"EPSG\",\"9739\"]]",
  "description": "EOS21-IRF",
  "authority": "EPSG",
  "version": "10.021(12.9.0)",
  "deprecated": "no",
  "areaname": "UK - Tweedmouth to Aberdeen",
  "extent": {
    "slat": 55.55,
    "nlat": 57.21,
    "llon": -3.56,
    "rlon": -1.94
  }
}