IGN 1987 - EPSG:5756

WKT

VERTCS["IGN_1987", 
	VDATUM["IGN_1987"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["IGN_1987", 
	VDATUM["IGN_1987"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "5756"]]

Data from @esri/proj-codes

{
  "wkid": 5756,
  "latestWkid": 5756,
  "macro": "PE_VCS_IGN_1987",
  "name": "IGN_1987",
  "wkt": "VERTCS[\"IGN_1987\",VDATUM[\"IGN_1987\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"IGN_1987\",VDATUM[\"IGN_1987\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"5756\"]]",
  "description": "IGN 1987",
  "authority": "EPSG",
  "version": "6.6(9.3.0.0)",
  "deprecated": "no",
  "areaname": "Martinique - onshore",
  "extent": {
    "slat": 14.35,
    "nlat": 14.93,
    "llon": -61.29,
    "rlon": -60.76
  }
}