diff --git a/openhtf/__init__.py b/openhtf/__init__.py
index 0dd2e3672..996c52002 100644
--- a/openhtf/__init__.py
+++ b/openhtf/__init__.py
@@ -14,6 +14,7 @@
 """The main OpenHTF entry point."""
 
 import signal
+import sys
 import typing
 
 from openhtf.core import phase_executor
@@ -112,6 +113,7 @@
 Subtest = openhtf.core.phase_collections.Subtest
 
 diagnose = openhtf.core.phase_descriptor.diagnose
+
 measures = openhtf.core.phase_descriptor.measures
 PhaseDescriptor = openhtf.core.phase_descriptor.PhaseDescriptor
 PhaseNameCase = openhtf.core.phase_descriptor.PhaseNameCase
@@ -147,3 +149,7 @@ def get_version():
 
 # Register signal handler to stop all tests on SIGINT.
 Test.DEFAULT_SIGINT_HANDLER = signal.signal(signal.SIGINT, Test.handle_sig_int)
+
+if sys.version_info.major == 3 and sys.version_info.minor >= 10:
+    import collections
+    setattr(collections, "MutableMapping", collections.abc.MutableMapping)
diff --git a/openhtf/core/dut_id.py b/openhtf/core/dut_id.py
new file mode 100644
index 000000000..35b2bde56
--- /dev/null
+++ b/openhtf/core/dut_id.py
@@ -0,0 +1,15 @@
+from dataclasses import dataclass
+from typing import Optional
+from dataclasses import dataclass
+
+
+@dataclass
+class DutIdentifier:
+    halter_serial_number: Optional [str] = None
+    mac_address: Optional[str] = None
+    part_number: Optional[str] = None
+    additional: Optional[dict] = None
+
+    @property
+    def test_id(self) -> str:
+        return self.halter_serial_number
diff --git a/openhtf/core/test_descriptor.py b/openhtf/core/test_descriptor.py
index 94aa466fa..649201253 100644
--- a/openhtf/core/test_descriptor.py
+++ b/openhtf/core/test_descriptor.py
@@ -45,6 +45,7 @@
 from openhtf.core import test_executor
 from openhtf.core import test_record as htf_test_record
 from openhtf.core import test_state
+from openhtf.core.dut_id import DutIdentifier
 
 from openhtf.util import configuration
 from openhtf.util import console_output
@@ -276,7 +277,9 @@ def abort_from_sig_int(self) -> None:
 
   def execute(self,
               test_start: Optional[Union[phase_descriptor.PhaseT,
-                                         Callable[[], str]]] = None,
+              Callable[[], str],
+              Callable[[], DutIdentifier],
+              ]] = None,
               profile_filename: Optional[Text] = None) -> bool:
     """Starts the framework and executes the given test.
 
@@ -300,7 +303,7 @@ def execute(self,
         self._test_desc.phase_sequence)
     # Lock this section so we don't .stop() the executor between instantiating
     # it and .Start()'ing it, doing so does weird things to the executor state.
-    with self._lock:
+    with (self._lock):
       # Sanity check to make sure someone isn't doing something weird like
       # trying to Execute() the same test twice in two separate threads.  We
       # hold the lock between here and Start()'ing the executor to guarantee
@@ -317,7 +320,13 @@ def execute(self,
 
         @phase_descriptor.PhaseOptions()
         def trigger_phase(test):
-          test.test_record.dut_id = typing.cast(types.LambdaType, test_start)()
+          dut_id = typing.cast(types.LambdaType, test_start)()
+          if isinstance(dut_id, DutIdentifier):
+            test.test_record.dut_id = dut_id.test_id
+            test.test_record.dut_extended_id = dut_id
+          else:
+            test.test_record.dut_id = dut_id
+            test.test_record.dut_extended_id = DutIdentifier()
 
         trigger = trigger_phase
       else:
diff --git a/openhtf/core/test_record.py b/openhtf/core/test_record.py
index bddce0357..1a387bdbb 100644
--- a/openhtf/core/test_record.py
+++ b/openhtf/core/test_record.py
@@ -16,6 +16,7 @@
 import enum
 import hashlib
 import inspect
+import json
 import logging
 import os
 import tempfile
@@ -24,6 +25,7 @@
 import attr
 
 from openhtf import util
+from openhtf.core.dut_id import DutIdentifier
 from openhtf.util import configuration
 from openhtf.util import data
 from openhtf.util import logs
@@ -167,6 +169,7 @@ class TestRecord(object):
   """The record of a single run of a test."""
 
   dut_id = attr.ib(type=Optional[Text])
+  dut_extended_id = attr.ib(type=Optional[DutIdentifier])
   station_id = attr.ib(type=Text)
   start_time_millis = attr.ib(type=int, default=0)
   end_time_millis = attr.ib(type=Optional[int], default=None)
@@ -250,6 +253,7 @@ def as_base_types(self) -> Dict[Text, Any]:
     metadata['config'] = self._cached_config_from_metadata
     ret = {
         'dut_id': data.convert_to_base_types(self.dut_id),
+        #'dut_extended_id': data.convert_to_base_types (self.dut_extended_id),
         'start_time_millis': self.start_time_millis,
         'end_time_millis': self.end_time_millis,
         'outcome': data.convert_to_base_types(self.outcome),
diff --git a/openhtf/core/test_state.py b/openhtf/core/test_state.py
index 3c408a77a..673b77eb9 100644
--- a/openhtf/core/test_state.py
+++ b/openhtf/core/test_state.py
@@ -174,6 +174,7 @@ def __init__(self, test_desc: 'test_descriptor.TestDescriptor',
 
     self.test_record = test_record.TestRecord(
         dut_id=None,
+        dut_extended_id=None,
         station_id=CONF.station_id,
         code_info=test_desc.code_info,
         start_time_millis=0,