EPSG:5714 — MSL height

VERTCRS[
    "MSL height",
    VDATUM["Mean Sea Level",ID["EPSG",5100]],
    CS[vertical,1,ID["EPSG",6499]],
    AXIS["Gravity-related height (H)",up],
    LENGTHUNIT["metre",1,ID["EPSG",9001]],
    ID["EPSG",5714]
]

+vunits=m +no_defs +type=crs

proj4.defs("EPSG:5714", "+vunits=m +no_defs +type=crs");

{
  "type": "CoordinateReferenceSystem",
  "code": 5714,
  "name": "MSL height",
  "kind": "vertical",
  "area": "World",
  "unit": "metre",
  "bbox": [
    -90,
    -180,
    90,
    180
  ],
  "proj4": "+vunits=m +no_defs +type=crs"
}

INSERT INTO spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext)
VALUES (5714, 'EPSG', 5714, '+vunits=m +no_defs +type=crs', 'VERT_CS["MSL height",VERT_DATUM["Mean Sea Level",2005,AUTHORITY["EPSG","5100"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["Gravity-related height",UP],AUTHORITY["EPSG","5714"]]');

PROJECTION
  "+vunits=m"
  "+no_defs"
  "+type=crs"
END

5714=VERT_CS["MSL height",VERT_DATUM["Mean Sea Level",2005,AUTHORITY["EPSG","5100"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["Gravity-related height",UP],AUTHORITY["EPSG","5714"]]