MGI 1901 - EPSG:3906

WKT

GEOGCS["GCS_MGI_1901", 
	DATUM["D_MGI_1901", 
		SPHEROID["Bessel_1841", 6377397.155, 299.1528128]], 
	PRIMEM["Greenwich", 0.0], 
	UNIT["Degree", 0.0174532925199433]]

WKT2

GEOGCRS["GCS_MGI_1901", 
	DATUM["D_MGI_1901", 
		ELLIPSOID["Bessel_1841", 6377397.155, 299.1528128]], 
	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", "3906"]]

Data from @esri/proj-codes

{
  "wkid": 3906,
  "latestWkid": 3906,
  "macro": "PE_GCS_MGI_1901",
  "name": "GCS_MGI_1901",
  "wkt": "GEOGCS[\"GCS_MGI_1901\",DATUM[\"D_MGI_1901\",SPHEROID[\"Bessel_1841\",6377397.155,299.1528128]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]",
  "wkt2": "GEOGCRS[\"GCS_MGI_1901\",DATUM[\"D_MGI_1901\",ELLIPSOID[\"Bessel_1841\",6377397.155,299.1528128]],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\",\"3906\"]]",
  "description": "MGI 1901",
  "authority": "EPSG",
  "version": "7.1(10.1.0)",
  "deprecated": "no",
  "areaname": "Europe - former Yugoslavia onshore",
  "extent": {
    "slat": 40.85,
    "nlat": 46.88,
    "llon": 13.38,
    "rlon": 23.04
  }
}