diff --git a/.github/workflows/unittests_old.yml b/.github/workflows/unittests_old.yml
index 530e10dd4..c8cb5716c 100644
--- a/.github/workflows/unittests_old.yml
+++ b/.github/workflows/unittests_old.yml
@@ -13,7 +13,7 @@ jobs:
     - name: Setup Mambaforge
       uses: conda-incubator/setup-miniconda@v3
       with:
-        python-version: '3.9'
+        python-version: '3.10'
         miniforge-variant: Mambaforge
         channels: conda-forge
         channel-priority: strict
diff --git a/pyiron_base/interfaces/has_dict.py b/pyiron_base/interfaces/has_dict.py
index e3eb01634..5e619df9b 100644
--- a/pyiron_base/interfaces/has_dict.py
+++ b/pyiron_base/interfaces/has_dict.py
@@ -16,6 +16,7 @@
 """
 
 from abc import ABC, abstractmethod
+from collections import defaultdict
 from typing import Any
 
 from pyiron_base.interfaces.has_hdf import HasHDF
@@ -54,7 +55,7 @@ def create_from_dict(obj_dict):
     type_field = obj_dict["TYPE"]
     module_path, class_name = _extract_module_class_name(type_field)
     class_object = _import_class(module_path, class_name)
-    version = obj_dict.get("VERSION", None)
+    version = obj_dict.get("DICT_VERSION", None)
     obj = class_object.instantiate(obj_dict, version)
     obj.from_dict(obj_dict, version)
     return obj
@@ -122,6 +123,9 @@ def load(inner_dict):
                 return {k: load(v) for k, v in inner_dict.items()}
             return create_from_dict(inner_dict)
 
+        obj_dict = self._split_children_dict(obj_dict)
+        if version is None:
+            version = obj_dict.get("DICT_VERSION", None)
         self._from_dict({k: load(v) for k, v in obj_dict.items()}, version)
 
     @abstractmethod
@@ -208,9 +212,28 @@ def _join_children_dict(children: dict[str, dict[str, Any]]) -> dict[str, Any]:
         return {
             "/".join((k1, k2)): v2
             for k1, v1 in children.items()
-            for k2, v2 in v2.items()
+            for k2, v2 in v1.items()
         }
 
+    @staticmethod
+    def _split_children_dict(
+        obj_dict: dict[str, Any],
+    ) -> dict[str, Any | dict[str, Any]]:
+        """
+        Undoes _join_children_dict.
+        """
+        subs = defaultdict(dict)
+        plain = {}
+        for k, v in obj_dict.items():
+            if "/" not in k:
+                plain[k] = v
+                continue
+            root, k = k.split("/", maxsplit=1)
+            subs[root][k] = v
+        # using update keeps type stability, i.e. we always return a plain dict
+        plain.update(subs)
+        return plain
+
 
 class HasHDFfromDict(HasHDF, HasDict):
     """
diff --git a/pyiron_base/storage/datacontainer.py b/pyiron_base/storage/datacontainer.py
index 46346c063..bba832713 100644
--- a/pyiron_base/storage/datacontainer.py
+++ b/pyiron_base/storage/datacontainer.py
@@ -40,6 +40,7 @@
     "HDF_VERSION",
     "DICT_VERSION",
     "READ_ONLY",
+    "KEY_ORDER",
 ]
 
 
@@ -827,6 +828,7 @@ def _on_unlock(self):
 
 
 class DataContainer(DataContainerBase, HasHDF, HasDict):
+    __dict_version__ = "0.2.0"
     __doc__ = f"""{DataContainerBase.__doc__}
 
     If instantiated with the argument `lazy=True`, data read from HDF5 later via :method:`.from_hdf` are not actually
@@ -1027,13 +1029,28 @@ def to(v):
         return data
 
     def _to_dict(self):
-        return {"data": self.to_builtin(), "READ_ONLY": self.read_only}
+        # stringify keys in case we are acting like a list
+        data = {str(k): v for k, v in dict(self).items()}
+        order = list(data)
+        data["READ_ONLY"] = self.read_only
+        data["KEY_ORDER"] = order
+        return data
 
     def _from_dict(self, obj_dict, version=None):
+        if version == "0.2.0":
+            order = obj_dict.pop("KEY_ORDER")
+        else:
+            order = None
+        self.read_only = obj_dict.pop("READ_ONLY", False)
+        for key in _internal_hdf_nodes:
+            obj_dict.pop(key, None)
         with self.unlocked():
             self.clear()
-            self.update(obj_dict["data"], wrap=True)
-        self.read_only = obj_dict.get("READ_ONLY", False)
+            if order is not None:
+                for key in order:
+                    self[key] = obj_dict[key]
+            else:
+                self.update(obj_dict)
 
 
 HDFStub.register(DataContainer, lambda h, g: h[g].to_object(lazy=True))
diff --git a/pyproject.toml b/pyproject.toml
index 8a590e0ea..6118082bd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,7 +18,6 @@ classifiers = [
     "License :: OSI Approved :: BSD License",
     "Intended Audience :: Science/Research",
     "Operating System :: OS Independent",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",