diff --git a/src/fmu/dataio/providers/_objectdata.py b/src/fmu/dataio/providers/_objectdata.py
index b4e038fc1..f5686f19a 100644
--- a/src/fmu/dataio/providers/_objectdata.py
+++ b/src/fmu/dataio/providers/_objectdata.py
@@ -133,42 +133,30 @@ def objectdata_provider_factory(
         metadata for.
     """
     if meta_existing:
-        return ExistingDataProvider(obj=obj, dataio=dataio, meta_existing=meta_existing)
-
-    meta_existing = {}
+        return ExistingDataProvider.from_metadata_dict(obj, dataio, meta_existing)
     if isinstance(obj, xtgeo.RegularSurface):
-        return RegularSurfaceDataProvider(
-            obj=obj, dataio=dataio, meta_existing=meta_existing
-        )
+        return RegularSurfaceDataProvider(obj=obj, dataio=dataio)
     if isinstance(obj, xtgeo.Polygons):
-        return PolygonsDataProvider(obj=obj, dataio=dataio, meta_existing=meta_existing)
+        return PolygonsDataProvider(obj=obj, dataio=dataio)
     if isinstance(obj, xtgeo.Points):
-        return PointsDataProvider(obj=obj, dataio=dataio, meta_existing=meta_existing)
+        return PointsDataProvider(obj=obj, dataio=dataio)
     if isinstance(obj, xtgeo.Cube):
-        return CubeDataProvider(obj=obj, dataio=dataio, meta_existing=meta_existing)
+        return CubeDataProvider(obj=obj, dataio=dataio)
     if isinstance(obj, xtgeo.Grid):
-        return CPGridDataProvider(obj=obj, dataio=dataio, meta_existing=meta_existing)
+        return CPGridDataProvider(obj=obj, dataio=dataio)
     if isinstance(obj, xtgeo.GridProperty):
-        return CPGridPropertyDataProvider(
-            obj=obj, dataio=dataio, meta_existing=meta_existing
-        )
+        return CPGridPropertyDataProvider(obj=obj, dataio=dataio)
     if isinstance(obj, pd.DataFrame):
-        return DataFrameDataProvider(
-            obj=obj, dataio=dataio, meta_existing=meta_existing
-        )
+        return DataFrameDataProvider(obj=obj, dataio=dataio)
     if isinstance(obj, dict):
-        return DictionaryDataProvider(
-            obj=obj, dataio=dataio, meta_existing=meta_existing
-        )
+        return DictionaryDataProvider(obj=obj, dataio=dataio)
 
     from pyarrow import Table
 
     if isinstance(obj, Table):
-        return ArrowTableDataProvider(
-            obj=obj, dataio=dataio, meta_existing=meta_existing
-        )
+        return ArrowTableDataProvider(obj=obj, dataio=dataio)
 
-    raise NotImplementedError("This data type is not (yet) supported: ", type(obj))
+    raise NotImplementedError(f"This data type is not currently supported: {type(obj)}")
 
 
 @dataclass
@@ -345,30 +333,33 @@ def get_objectdata(self) -> DerivedObjectDescriptor:
 
 @dataclass
 class ExistingDataProvider(ObjectDataProvider):
-    """These functions should never be called because derive_metadata will populate the
-    object data from existing metadata, by calling _derive_from_existing, and return
-    before calling them."""
+    """These getters should never be called because metadata was derived a priori."""
 
-    obj: Any
+    obj: Inferrable
 
-    def get_spec(self) -> dict[str, Any]:
+    def get_spec(self) -> dict:
         """Derive data.spec from existing metadata."""
-        return self.meta_existing["spec"]
+        return self.metadata["spec"]
 
-    def get_bbox(self) -> dict[str, Any]:
+    def get_bbox(self) -> dict:
         """Derive data.bbox from existing metadata."""
-        return self.meta_existing["bbox"]
+        return self.metadata["bbox"]
 
     def get_objectdata(self) -> DerivedObjectDescriptor:
         """Derive object data for existing metadata."""
         return DerivedObjectDescriptor(
-            subtype=self.meta_existing["subtype"],
-            classname=self.meta_existing["class"],
-            layout=self.meta_existing["layout"],
+            subtype=self.metadata["subtype"],
+            classname=self.metadata["class"],
+            layout=self.metadata["layout"],
             efolder=self.efolder,
-            fmt=self.meta_existing["format"],
+            fmt=self.fmt,
             extension=self.extension,
             spec=self.get_spec(),
             bbox=self.get_bbox(),
             table_index=None,
         )
+
+    def derive_metadata(self) -> None:
+        """Metadata has already been derived for this provider, and is already set from
+        instantiation, so override this method and do nothing."""
+        return
diff --git a/src/fmu/dataio/providers/_objectdata_base.py b/src/fmu/dataio/providers/_objectdata_base.py
index 8b7ed938d..8617df105 100644
--- a/src/fmu/dataio/providers/_objectdata_base.py
+++ b/src/fmu/dataio/providers/_objectdata_base.py
@@ -4,7 +4,7 @@
 from dataclasses import dataclass, field
 from datetime import datetime
 from pathlib import Path
-from typing import Any, Dict, Final, Literal, Optional, TypeVar
+from typing import TYPE_CHECKING, Any, Dict, Final, Literal, Optional, TypeVar
 from warnings import warn
 
 from fmu.dataio import dataio, types
@@ -14,6 +14,10 @@
 from fmu.dataio.datastructure._internal.internal import AllowedContent
 from fmu.dataio.datastructure.meta import content
 
+if TYPE_CHECKING:
+    from fmu.dataio.dataio import ExportData
+    from fmu.dataio.types import Inferrable
+
 logger: Final = null_logger(__name__)
 
 V = TypeVar("V")
@@ -126,21 +130,16 @@ class ObjectDataProvider(ABC):
     # input fields
     obj: types.Inferrable
     dataio: dataio.ExportData
-    meta_existing: dict = field(default_factory=dict)
 
     # result properties; the most important is metadata which IS the 'data' part in
     # the resulting metadata. But other variables needed later are also given
     # as instance properties in addition (for simplicity in other classes/functions)
-    bbox: dict = field(default_factory=dict)
+    metadata: dict = field(default_factory=dict)
+    name: str = field(default="")
     classname: str = field(default="")
     efolder: str = field(default="")
     extension: str = field(default="")
     fmt: str = field(default="")
-    layout: str = field(default="")
-    metadata: dict = field(default_factory=dict)
-    name: str = field(default="")
-    specs: dict = field(default_factory=dict)
-    subtype: str = field(default="")
     time0: str | None = field(default=None)
     time1: str | None = field(default=None)
 
@@ -255,35 +254,22 @@ def _derive_timedata(self) -> Optional[dict[str, str]]:
             mode="json", exclude_none=True
         )
 
-    def _derive_from_existing(self) -> None:
-        """Derive from existing metadata."""
-
-        # do not change any items in 'data' block, as it may ruin e.g. stratigrapical
-        # setting (i.e. changing data.name is not allowed)
-        self.metadata = self.meta_existing["data"]
-        self.name = self.meta_existing["data"]["name"]
-
-        # derive the additional attributes needed later e.g. in Filedata provider:
-        relpath = Path(self.meta_existing["file"]["relative_path"])
-        if self.dataio.subfolder:
-            self.efolder = relpath.parent.parent.name
-        else:
-            self.efolder = relpath.parent.name
+    @abstractmethod
+    def get_spec(self) -> dict:
+        raise NotImplementedError
 
-        self.classname = self.meta_existing["class"]
-        self.extension = relpath.suffix
-        self.fmt = self.meta_existing["data"]["format"]
+    @abstractmethod
+    def get_bbox(self) -> dict:
+        raise NotImplementedError
 
-        self.time0, self.time1 = parse_timedata(self.meta_existing["data"])
+    @abstractmethod
+    def get_objectdata(self) -> DerivedObjectDescriptor:
+        raise NotImplementedError
 
     def derive_metadata(self) -> None:
         """Main function here, will populate the metadata block for 'data'."""
         logger.info("Derive all metadata for data object...")
 
-        if self.meta_existing:
-            self._derive_from_existing()
-            return
-
         namedstratigraphy = self._derive_name_stratigraphy()
         objres = self.get_objectdata()
         if self.dataio.forcefolder and not self.dataio.forcefolder.startswith("/"):
@@ -341,14 +327,26 @@ def derive_metadata(self) -> None:
         self.fmt = objres.fmt
         logger.info("Derive all metadata for data object... DONE")
 
-    @abstractmethod
-    def get_spec(self) -> dict[str, Any]:
-        raise NotImplementedError
-
-    @abstractmethod
-    def get_bbox(self) -> dict[str, Any]:
-        raise NotImplementedError
-
-    @abstractmethod
-    def get_objectdata(self) -> DerivedObjectDescriptor:
-        raise NotImplementedError
+    @classmethod
+    def from_metadata_dict(
+        cls, obj: Inferrable, dataio: ExportData, meta_existing: dict
+    ) -> ObjectDataProvider:
+        """Instantiate from existing metadata."""
+
+        relpath = Path(meta_existing["file"]["relative_path"])
+        time0, time1 = parse_timedata(meta_existing["data"])
+
+        return cls(
+            obj=obj,
+            dataio=dataio,
+            metadata=meta_existing["data"],
+            name=meta_existing["data"]["name"],
+            classname=meta_existing["class"],
+            efolder=(
+                relpath.parent.parent.name if dataio.subfolder else relpath.parent.name
+            ),
+            extension=relpath.suffix,
+            fmt=meta_existing["data"]["format"],
+            time0=time0,
+            time1=time1,
+        )
diff --git a/tests/test_units/test_objectdataprovider_class.py b/tests/test_units/test_objectdataprovider_class.py
index c7fb71890..932f92cfa 100644
--- a/tests/test_units/test_objectdataprovider_class.py
+++ b/tests/test_units/test_objectdataprovider_class.py
@@ -1,8 +1,18 @@
 """Test the _ObjectData class from the _objectdata.py module"""
 
+import os
+
 import pytest
+from fmu.dataio import dataio
 from fmu.dataio._definitions import ConfigurationError, ValidFormats
-from fmu.dataio.providers._objectdata import objectdata_provider_factory
+from fmu.dataio._metadata import MetaData
+from fmu.dataio.providers._objectdata import (
+    ExistingDataProvider,
+    objectdata_provider_factory,
+)
+from fmu.dataio.providers._objectdata_xtgeo import RegularSurfaceDataProvider
+
+from ..utils import inside_rms
 
 # --------------------------------------------------------------------------------------
 # RegularSurface
@@ -67,8 +77,10 @@ def test_objectdata_regularsurface_spec_bbox(regsurf, edataobj1):
 def test_objectdata_regularsurface_derive_objectdata(regsurf, edataobj1):
     """Derive other properties."""
 
-    res = objectdata_provider_factory(regsurf, edataobj1).get_objectdata()
+    objdata = objectdata_provider_factory(regsurf, edataobj1)
+    assert isinstance(objdata, RegularSurfaceDataProvider)
 
+    res = objdata.get_objectdata()
     assert res.subtype == "RegularSurface"
     assert res.classname == "surface"
     assert res.extension == ".gri"
@@ -81,5 +93,68 @@ def test_objectdata_regularsurface_derive_metadata(regsurf, edataobj1):
     myobj.derive_metadata()
     res = myobj.metadata
     assert res["content"] == "depth"
-
     assert res["alias"]
+
+
+def test_objectdata_provider_factory_raises_on_unknown(edataobj1):
+    with pytest.raises(NotImplementedError, match="not currently supported"):
+        objectdata_provider_factory(object(), edataobj1)
+
+
+def test_regsurf_preprocessed_observation(
+    fmurun_w_casemetadata, rmssetup, rmsglobalconfig, regsurf
+):
+    """Test generating pre-realization surfaces that comes to share/preprocessed.
+
+    Later, a fmu run will update this (merge metadata)
+    """
+
+    @inside_rms
+    def _export_data_from_rms(rmssetup, rmsglobalconfig, regsurf):
+        """Run an export of a preprocessed surface inside RMS."""
+
+        os.chdir(rmssetup)
+        edata = dataio.ExportData(
+            config=rmsglobalconfig,  # read from global config
+            fmu_context="preprocessed",
+            name="TopVolantis",
+            content="depth",
+            is_observation=True,
+            timedata=[[20240802, "moni"], [20200909, "base"]],
+        )
+        return edata, edata.export(regsurf)
+
+    def _run_case_fmu(fmurun_w_casemetadata, rmsglobalconfig, surfacepath):
+        """Run FMU workflow, using the preprocessed data as case data.
+
+        When re-using metadata, the input object to dataio shall not be a XTGeo or
+        Pandas or ... instance, but just a file path (either as string or a pathlib.Path
+        object). This is because we want to avoid time and resources spent on double
+        reading e.g. a seismic cube, but rather trigger a file copy action instead.
+
+        But it requires that valid metadata for that file is found. The rule for
+        merging is currently defaulted to "preprocessed".
+        """
+        os.chdir(fmurun_w_casemetadata)
+
+        casepath = fmurun_w_casemetadata.parent.parent
+        edata = dataio.ExportData(
+            config=rmsglobalconfig,
+            fmu_context="case",
+            content=None,
+            is_observation=True,
+        )
+        _ = edata.generate_metadata(
+            surfacepath,
+            casepath=casepath,
+        )
+        metaobj = MetaData(surfacepath, edata)
+        metaobj._populate_meta_objectdata()
+        assert isinstance(metaobj.objdata, ExistingDataProvider)
+        return metaobj
+
+    # run two stage process
+    edata, mysurf = _export_data_from_rms(rmssetup, rmsglobalconfig, regsurf)
+    metaobj = _run_case_fmu(fmurun_w_casemetadata, rmsglobalconfig, mysurf)
+    case_meta = metaobj.generate_export_metadata()
+    assert edata._metadata["data"] == case_meta["data"]