Baltic depth - EPSG:5612

WKT

VERTCS["Baltic_depth", 
	VDATUM["Baltic_Sea"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", -1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["Baltic_depth", 
	VDATUM["Baltic_Sea"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", down, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "5612"]]

Data from @esri/proj-codes

{
  "wkid": 5612,
  "latestWkid": 5612,
  "macro": "PE_VCS_BALTIC_DEPTH",
  "name": "Baltic_depth",
  "wkt": "VERTCS[\"Baltic_depth\",VDATUM[\"Baltic_Sea\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",-1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"Baltic_depth\",VDATUM[\"Baltic_Sea\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",down,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"5612\"]]",
  "description": "Baltic depth",
  "authority": "EPSG",
  "version": "9.2.2(10.0.0)",
  "deprecated": "no",
  "areaname": "Europe - FSU, Czechoslovakia - onshore",
  "extent": {
    "slat": 35.14,
    "nlat": 77.79,
    "llon": 12.09,
    "rlon": -169.57
  }
}