diff --git a/lib/iris/_concatenate.py b/lib/iris/_concatenate.py
index d98e63da5a..7bb27eaf83 100644
--- a/lib/iris/_concatenate.py
+++ b/lib/iris/_concatenate.py
@@ -115,9 +115,9 @@ def __new__(mcs, coord, dims):
             kwargs["circular"] = coord.circular
         if isinstance(coord, iris.coords.DimCoord):
             # Mix the monotonic ordering into the metadata.
-            if coord.core_points()[0] == coord.core_points()[-1]:
+            if coord.points[0] == coord.points[-1]:
                 order = _CONSTANT
-            elif coord.core_points()[-1] > coord.core_points()[0]:
+            elif coord.points[-1] > coord.points[0]:
                 order = _INCREASING
             else:
                 order = _DECREASING
@@ -775,37 +775,21 @@ def _calculate_extents(self):
         self.dim_extents = []
         for coord, order in zip(self.dim_coords, self.dim_order):
             if order == _CONSTANT or order == _INCREASING:
-                points = _Extent(
-                    coord.core_points()[0], coord.core_points()[-1]
-                )
-                if coord.core_bounds() is not None:
+                points = _Extent(coord.points[0], coord.points[-1])
+                if coord.bounds is not None:
                     bounds = (
-                        _Extent(
-                            coord.core_bounds()[0, 0],
-                            coord.core_bounds()[-1, 0],
-                        ),
-                        _Extent(
-                            coord.core_bounds()[0, 1],
-                            coord.core_bounds()[-1, 1],
-                        ),
+                        _Extent(coord.bounds[0, 0], coord.bounds[-1, 0]),
+                        _Extent(coord.bounds[0, 1], coord.bounds[-1, 1]),
                     )
                 else:
                     bounds = None
             else:
                 # The order must be decreasing ...
-                points = _Extent(
-                    coord.core_points()[-1], coord.core_points()[0]
-                )
-                if coord.core_bounds() is not None:
+                points = _Extent(coord.points[-1], coord.points[0])
+                if coord.bounds is not None:
                     bounds = (
-                        _Extent(
-                            coord.core_bounds()[-1, 0],
-                            coord.core_bounds()[0, 0],
-                        ),
-                        _Extent(
-                            coord.core_bounds()[-1, 1],
-                            coord.core_bounds()[0, 1],
-                        ),
+                        _Extent(coord.bounds[-1, 0], coord.bounds[0, 0]),
+                        _Extent(coord.bounds[-1, 1], coord.bounds[0, 1]),
                     )
                 else:
                     bounds = None
diff --git a/lib/iris/tests/unit/concatenate/__init__.py b/lib/iris/tests/unit/concatenate/__init__.py
index cf671a6553..229476f3a6 100644
--- a/lib/iris/tests/unit/concatenate/__init__.py
+++ b/lib/iris/tests/unit/concatenate/__init__.py
@@ -3,4 +3,138 @@
 # This file is part of Iris and is released under the LGPL license.
 # See COPYING and COPYING.LESSER in the root of the repository for full
 # licensing details.
-"""Unit tests for the :mod:`iris._concatenate` package."""
+"""Unit-test infrastructure for the :mod:`iris._concatenate` package."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any
+
+import dask.array as da
+import numpy as np
+
+from iris._concatenate import _CONSTANT, _DECREASING, _INCREASING
+import iris.common
+from iris.coords import AuxCoord, DimCoord
+
+__all__ = ["ExpectedItem", "N_POINTS", "SCALE_FACTOR", "create_metadata"]
+
+# number of coordinate points
+N_POINTS: int = 10
+
+# coordinate points multiplication scale factor
+SCALE_FACTOR: int = 10
+
+
+METADATA = {
+    "standard_name": "air_temperature",
+    "long_name": "air temperature",
+    "var_name": "atemp",
+    "units": "kelvin",
+    "attributes": {},
+    "coord_system": None,
+    "climatological": False,
+    "circular": False,
+}
+
+
+@dataclass
+class ExpectedItem:
+    """Expected test result components of :class:`iris._concatenate._CoordMetaData`."""
+
+    defn: iris.common.DimCoordMetadata | iris.common.CoordMetadata
+    dims: tuple[int, ...]
+    points_dtype: np.dtype
+    bounds_dtype: np.dtype | None = None
+    kwargs: dict[str, Any] = field(default_factory=dict)
+
+
+@dataclass
+class MetaDataItem:
+    """Test input and expected output from :class:`iris._concatenate._CoordMetaData`."""
+
+    coord: AuxCoord | DimCoord
+    dims: tuple[int, ...]
+    expected: ExpectedItem
+
+
+def create_metadata(
+    dim_coord: bool = True,
+    scalar: bool = False,
+    order: int = None,
+    circular: bool | None = False,
+    coord_dtype: np.dtype = None,
+    lazy: bool = True,
+    with_bounds: bool | None = False,
+) -> MetaDataItem:
+    """Construct payload for :class:`iris._concatenate.CoordMetaData` testing."""
+    if coord_dtype is None:
+        coord_dtype = np.float32
+
+    if order is None:
+        order = _INCREASING
+
+    array_lib = da if lazy else np
+    bounds = None
+
+    if scalar:
+        points = array_lib.ones(1, dtype=coord_dtype)
+        order = _CONSTANT
+
+        if with_bounds:
+            bounds = array_lib.array([0, 2], dtype=coord_dtype).reshape(1, 2)
+    else:
+        if order == _CONSTANT:
+            points = array_lib.ones(N_POINTS, dtype=coord_dtype)
+        else:
+            if order == _DECREASING:
+                start, stop, step = N_POINTS - 1, -1, -1
+            else:
+                start, stop, step = 0, N_POINTS, 1
+            points = (
+                array_lib.arange(start, stop, step, dtype=coord_dtype)
+                * SCALE_FACTOR
+            )
+
+        if with_bounds:
+            offset = SCALE_FACTOR // 2
+            bounds = array_lib.vstack(
+                [points.copy() - offset, points.copy() + offset]
+            ).T
+
+    bounds_dtype = coord_dtype if with_bounds else None
+
+    values = METADATA.copy()
+    values["circular"] = circular
+    CoordClass = DimCoord if dim_coord else AuxCoord
+    coord = CoordClass(points, bounds=bounds)
+    if dim_coord and lazy:
+        # creating a DimCoord *always* results in realized points/bounds.
+        assert not coord.has_lazy_points()
+        if with_bounds:
+            assert not coord.has_lazy_bounds()
+    metadata = iris.common.DimCoordMetadata(**values)
+
+    if dim_coord:
+        coord.metadata = metadata
+    else:
+        # convert the DimCoordMetadata to a CoordMetadata instance
+        # and assign to the AuxCoord
+        coord.metadata = iris.common.CoordMetadata.from_metadata(metadata)
+
+    dims = tuple([dim for dim in range(coord.ndim)])
+    kwargs = {"scalar": scalar}
+
+    if dim_coord:
+        kwargs["circular"] = circular
+        kwargs["order"] = order
+
+    expected = ExpectedItem(
+        defn=metadata,
+        dims=dims,
+        points_dtype=coord_dtype,
+        bounds_dtype=bounds_dtype,
+        kwargs=kwargs,
+    )
+
+    return MetaDataItem(coord=coord, dims=dims, expected=expected)
diff --git a/lib/iris/tests/unit/concatenate/test__CoordMetaData.py b/lib/iris/tests/unit/concatenate/test__CoordMetaData.py
new file mode 100644
index 0000000000..6f29e1f65f
--- /dev/null
+++ b/lib/iris/tests/unit/concatenate/test__CoordMetaData.py
@@ -0,0 +1,117 @@
+# Copyright Iris contributors
+#
+# This file is part of Iris and is released under the LGPL license.
+# See COPYING and COPYING.LESSER in the root of the repository for full
+# licensing details.
+"""Unit-tests for :class:`iris._concatenate._CoordMetaData`."""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+from iris._concatenate import (
+    _CONSTANT,
+    _DECREASING,
+    _INCREASING,
+    _CoordMetaData,
+)
+
+from . import ExpectedItem, create_metadata
+
+
+def check(actual: _CoordMetaData, expected: ExpectedItem) -> None:
+    """Assert actual and expected results."""
+    assert actual.defn == expected.defn
+    assert actual.dims == expected.dims
+    assert actual.points_dtype == expected.points_dtype
+    assert actual.bounds_dtype == expected.bounds_dtype
+    assert actual.kwargs == expected.kwargs
+
+
+@pytest.mark.parametrize("order", [_DECREASING, _INCREASING])
+@pytest.mark.parametrize("circular", [False, True])
+@pytest.mark.parametrize("coord_dtype", [np.int32, np.float32])
+@pytest.mark.parametrize("lazy", [False, True])
+@pytest.mark.parametrize("with_bounds", [False, True])
+def test_dim(
+    order: int,
+    circular: bool,
+    coord_dtype: np.dtype,
+    lazy: bool,
+    with_bounds: bool,
+) -> None:
+    """Test :class:`iris._concatenate._CoordMetaData` with dim coord."""
+    metadata = create_metadata(
+        dim_coord=True,
+        scalar=False,
+        order=order,
+        circular=circular,
+        coord_dtype=coord_dtype,
+        lazy=lazy,
+        with_bounds=with_bounds,
+    )
+    actual = _CoordMetaData(coord=metadata.coord, dims=metadata.dims)
+    check(actual, metadata.expected)
+
+
+@pytest.mark.parametrize("circular", [False, True])
+@pytest.mark.parametrize("coord_dtype", [np.int32, np.float32])
+@pytest.mark.parametrize("lazy", [False, True])
+@pytest.mark.parametrize("with_bounds", [False, True])
+def test_dim__scalar(
+    circular: bool, coord_dtype: np.dtype, lazy: bool, with_bounds: bool
+) -> None:
+    """Test :class:`iris._concatenate._CoordMetaData` with scalar dim coord."""
+    metadata = create_metadata(
+        dim_coord=True,
+        scalar=True,
+        order=_CONSTANT,
+        circular=circular,
+        coord_dtype=coord_dtype,
+        lazy=lazy,
+        with_bounds=with_bounds,
+    )
+    actual = _CoordMetaData(coord=metadata.coord, dims=metadata.dims)
+    check(actual, metadata.expected)
+
+
+@pytest.mark.parametrize("order", [_DECREASING, _INCREASING])
+@pytest.mark.parametrize("coord_dtype", [np.int32, np.float32])
+@pytest.mark.parametrize("lazy", [False, True])
+@pytest.mark.parametrize("with_bounds", [False, True])
+def test_aux(
+    order: int, coord_dtype: np.dtype, lazy: bool, with_bounds: bool
+) -> None:
+    """Test :class:`iris._concatenate._CoordMetaData` with aux coord."""
+    metadata = create_metadata(
+        dim_coord=False,
+        scalar=False,
+        order=order,
+        circular=None,
+        coord_dtype=coord_dtype,
+        lazy=lazy,
+        with_bounds=with_bounds,
+    )
+    actual = _CoordMetaData(coord=metadata.coord, dims=metadata.dims)
+    check(actual, metadata.expected)
+
+
+@pytest.mark.parametrize("coord_dtype", [np.int32, np.float32])
+@pytest.mark.parametrize("lazy", [False, True])
+@pytest.mark.parametrize("with_bounds", [False, True])
+def test_aux__scalar(
+    coord_dtype: np.dtype, lazy: bool, with_bounds: bool
+) -> None:
+    """Test :class:`iris._concatenate._CoordMetaData` with scalar aux coord."""
+    metadata = create_metadata(
+        dim_coord=False,
+        scalar=True,
+        order=_CONSTANT,
+        circular=None,
+        coord_dtype=coord_dtype,
+        lazy=lazy,
+        with_bounds=with_bounds,
+    )
+    actual = _CoordMetaData(coord=metadata.coord, dims=metadata.dims)
+    check(actual, metadata.expected)
diff --git a/lib/iris/tests/unit/concatenate/test__CoordSignature.py b/lib/iris/tests/unit/concatenate/test__CoordSignature.py
new file mode 100644
index 0000000000..eb62c5ec64
--- /dev/null
+++ b/lib/iris/tests/unit/concatenate/test__CoordSignature.py
@@ -0,0 +1,121 @@
+# Copyright Iris contributors
+#
+# This file is part of Iris and is released under the LGPL license.
+# See COPYING and COPYING.LESSER in the root of the repository for full
+# licensing details.
+"""Unit-tests for :class:`iris._concatenate._CoordSignature`."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+
+import numpy as np
+import pytest
+
+from iris._concatenate import (
+    _CONSTANT,
+    _DECREASING,
+    _INCREASING,
+    _CoordExtent,
+    _CoordMetaData,
+    _CoordSignature,
+    _Extent,
+)
+from iris.coords import DimCoord
+
+from . import N_POINTS, SCALE_FACTOR, create_metadata
+
+
+@dataclass
+class MockCubeSignature:
+    """Simple mock of :class:`iris._concatenate._CubeSignature`."""
+
+    aux_coords_and_dims: bool | None = None
+    cell_measures_and_dims: bool | None = None
+    ancillary_variables_and_dims: bool | None = None
+    derived_coords_and_dims: bool | None = None
+    dim_coords: list[DimCoord, ...] = field(default_factory=list)
+    dim_mapping: bool | None = None
+    dim_extents: list[_Extent, ...] = field(default_factory=list)
+    dim_order: list[int, ...] = field(default_factory=list)
+    dim_metadata: list[_CoordMetaData, ...] = field(default_factory=list)
+
+
+@pytest.mark.parametrize("order", [_DECREASING, _INCREASING])
+@pytest.mark.parametrize("coord_dtype", [np.int32, np.float32])
+@pytest.mark.parametrize("lazy", [False, True])
+@pytest.mark.parametrize("with_bounds", [False, True])
+def test_dim(
+    order: int, coord_dtype: np.dtype, lazy: bool, with_bounds: bool
+) -> None:
+    """Test extent calculation of vector dimension coordinates."""
+    metadata = create_metadata(
+        dim_coord=True,
+        scalar=False,
+        order=order,
+        coord_dtype=coord_dtype,
+        lazy=lazy,
+        with_bounds=with_bounds,
+    )
+    dim_metadata = [_CoordMetaData(metadata.coord, metadata.dims)]
+    cube_signature = MockCubeSignature(
+        dim_coords=[metadata.coord], dim_metadata=dim_metadata
+    )
+    coord_signature = _CoordSignature(cube_signature)
+    assert len(coord_signature.dim_extents) == 1
+    (actual,) = coord_signature.dim_extents
+    first, last = coord_dtype(0), coord_dtype((N_POINTS - 1) * SCALE_FACTOR)
+    if order == _CONSTANT:
+        emsg = f"Expected 'order' of '{_DECREASING}' or '{_INCREASING}', got '{order}'."
+        raise ValueError(emsg)
+    points_extent = _Extent(min=first, max=last)
+    bounds_extent = None
+    if with_bounds:
+        offset = SCALE_FACTOR // 2
+        if order == _INCREASING:
+            bounds_extent = (
+                _Extent(min=first - offset, max=last - offset),
+                _Extent(min=first + offset, max=last + offset),
+            )
+        else:
+            bounds_extent = (
+                _Extent(min=first + offset, max=last + offset),
+                _Extent(min=first - offset, max=last - offset),
+            )
+    expected = _CoordExtent(points=points_extent, bounds=bounds_extent)
+    assert actual == expected
+
+
+@pytest.mark.parametrize("coord_dtype", [np.int32, np.float32])
+@pytest.mark.parametrize("lazy", [False, True])
+@pytest.mark.parametrize("with_bounds", [False, True])
+def test_dim__scalar(
+    coord_dtype: np.dtype, lazy: bool, with_bounds: bool
+) -> None:
+    """Test extent calculation of scalar dimension coordinates."""
+    metadata = create_metadata(
+        dim_coord=True,
+        scalar=True,
+        order=_CONSTANT,
+        coord_dtype=coord_dtype,
+        lazy=lazy,
+        with_bounds=with_bounds,
+    )
+    dim_metadata = [_CoordMetaData(metadata.coord, metadata.dims)]
+    cube_signature = MockCubeSignature(
+        dim_coords=[metadata.coord], dim_metadata=dim_metadata
+    )
+    coord_signature = _CoordSignature(cube_signature)
+    assert len(coord_signature.dim_extents) == 1
+    (actual,) = coord_signature.dim_extents
+    point = coord_dtype(1)
+    points_extent = _Extent(min=point, max=point)
+    bounds_extent = None
+    if with_bounds:
+        first, last = coord_dtype(0), coord_dtype(2)
+        bounds_extent = (
+            _Extent(min=first, max=first),
+            _Extent(min=last, max=last),
+        )
+    expected = _CoordExtent(points=points_extent, bounds=bounds_extent)
+    assert actual == expected