EPSG:8052 — MSL height (ftUS)

VERTCRS[
    "MSL height (ftUS)",
    BASEVERTCRS[
        "MSL height",
        VDATUM["Mean Sea Level",ID["EPSG",5100]],
        ID["EPSG",5714]
    ],
    DERIVINGCONVERSION[
        "Vertical Axis Unit Conversion",
        METHOD["Change of Vertical Unit",ID["EPSG",1104]],
        ID["EPSG",7813]
    ],
    CS[vertical,1,ID["EPSG",6497]],
    AXIS["Gravity-related height (H)",up],
    LENGTHUNIT["US survey foot",0.304800609601219,ID["EPSG",9003]],
    ID["EPSG",8052]
]

+vunits=us-ft +no_defs +type=crs

proj4.defs("EPSG:8052", "+vunits=us-ft +no_defs +type=crs");

{
  "type": "CoordinateReferenceSystem",
  "code": 8052,
  "name": "MSL height (ftUS)",
  "kind": "vertical",
  "area": "USA",
  "unit": "US survey foot",
  "bbox": [
    15.56,
    167.65,
    74.71,
    -65.69
  ],
  "proj4": "+vunits=us-ft +no_defs +type=crs"
}

INSERT INTO spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext)
VALUES (8052, 'EPSG', 8052, '+vunits=us-ft +no_defs +type=crs', 'VERT_CS["MSL height (ftUS)",VERT_DATUM["Mean Sea Level",2005,AUTHORITY["EPSG","5100"]],UNIT["US survey foot",0.304800609601219,AUTHORITY["EPSG","9003"]],AXIS["Gravity-related height",UP],AUTHORITY["EPSG","8052"]]');

PROJECTION
  "+vunits=us-ft"
  "+no_defs"
  "+type=crs"
END

8052=VERT_CS["MSL height (ftUS)",VERT_DATUM["Mean Sea Level",2005,AUTHORITY["EPSG","5100"]],UNIT["US survey foot",0.304800609601219,AUTHORITY["EPSG","9003"]],AXIS["Gravity-related height",UP],AUTHORITY["EPSG","8052"]]