FNL22 Grid - EPSG:9977

WKT

PROJCS["FNL22_Grid", 
	GEOGCS["FNL22-IRF", 
		DATUM["FNL22_Intermediate_Reference_Frame", 
			SPHEROID["GRS_1980", 6378137.0, 298.257222101]], 
		PRIMEM["Greenwich", 0.0], 
		UNIT["Degree", 0.0174532925199433]], 
	PROJECTION["Transverse_Mercator"], 
	PARAMETER["False_Easting", 139618.9493], 
	PARAMETER["False_Northing", 183110.794], 
	PARAMETER["Central_Meridian", -3.8], 
	PARAMETER["Scale_Factor", 1.0], 
	PARAMETER["Latitude_Of_Origin", 58.0], 
	UNIT["Meter", 1.0]]

WKT2

PROJCRS["FNL22_Grid", 
	BASEGEOGCRS["FNL22-IRF", 
		DATUM["FNL22_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]], 
	CONVERSION["Transverse_Mercator", 
		METHOD["Transverse_Mercator"], 
		PARAMETER["False_Easting", 139618.9493], 
		PARAMETER["False_Northing", 183110.794], 
		PARAMETER["Central_Meridian", -3.8], 
		PARAMETER["Scale_Factor", 1.0], 
		PARAMETER["Latitude_Of_Origin", 58.0]], 
	CS[Cartesian, 2], 
	AXIS["Easting (X)", east, 
		ORDER[1]], 
	AXIS["Northing (Y)", north, 
		ORDER[2]], 
	LENGTHUNIT["Meter", 1.0], 
	ID["EPSG", "9977"]]

Data from @esri/proj-codes

{
  "wkid": 9977,
  "latestWkid": 9977,
  "gcsWkid": 9974,
  "macro": "PE_PCS_FNL22_GRID",
  "name": "FNL22_Grid",
  "wkt": "PROJCS[\"FNL22_Grid\",GEOGCS[\"FNL22-IRF\",DATUM[\"FNL22_Intermediate_Reference_Frame\",SPHEROID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]],PROJECTION[\"Transverse_Mercator\"],PARAMETER[\"False_Easting\",139618.9493],PARAMETER[\"False_Northing\",183110.794],PARAMETER[\"Central_Meridian\",-3.8],PARAMETER[\"Scale_Factor\",1.0],PARAMETER[\"Latitude_Of_Origin\",58.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "PROJCRS[\"FNL22_Grid\",BASEGEOGCRS[\"FNL22-IRF\",DATUM[\"FNL22_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]],CONVERSION[\"Transverse_Mercator\",METHOD[\"Transverse_Mercator\"],PARAMETER[\"False_Easting\",139618.9493],PARAMETER[\"False_Northing\",183110.794],PARAMETER[\"Central_Meridian\",-3.8],PARAMETER[\"Scale_Factor\",1.0],PARAMETER[\"Latitude_Of_Origin\",58.0]],CS[Cartesian,2],AXIS[\"Easting (X)\",east,ORDER[1]],AXIS[\"Northing (Y)\",north,ORDER[2]],LENGTHUNIT[\"Meter\",1.0],ID[\"EPSG\",\"9977\"]]",
  "description": "FNL22 Grid",
  "authority": "EPSG",
  "version": "10.059(13.1.0)",
  "deprecated": "no",
  "areaname": "UK - Inverness to Thurso",
  "extent": {
    "slat": 57.4,
    "nlat": 58.64,
    "llon": -4.6,
    "rlon": -3
  }
}