diff --git a/src/cal_tools/calcat_interface2.py b/src/cal_tools/calcat_interface2.py
index 3ec10de53e73bc83f90a256e95bd90c52ec4e6ed..4f0c9d30c7325eacea23bf94e3b88b32797d7a05 100644
--- a/src/cal_tools/calcat_interface2.py
+++ b/src/cal_tools/calcat_interface2.py
@@ -201,7 +201,7 @@ def setup_client(
     if oauth_client is None and base_url == CALCAT_PROXY_URL:
         try:
             # timeout=(connect_timeout, read_timeout)
-            global_client.get_request('me', timeout=(1, 5))
+            global_client.get_request("me", timeout=(1, 5))
         except requests.ConnectionError as e:
             raise RuntimeError(
                 "Could not connect to calibration catalog proxy. This proxy allows "
@@ -309,12 +309,45 @@ def prepare_selection(
 
 
 @dataclass
-class MultiModuleConstant:
+class MultiModuleConstant(Mapping):
     """A group of similar constants for several modules of one detector"""
 
     constants: Dict[str, SingleConstant]  # Keys e.g. 'LPD00'
     module_details: List[Dict]
     detector_name: str  # e.g. 'HED_DET_AGIPD500K2G'
+    calibration_name: str
+
+    def __repr__(self):
+        return (
+            f"<MultiModuleConstant: {self.calibration_name} for "
+            f"{len(self.constants)} modules of {self.detector_name}>"
+        )
+
+    def __iter__(self):
+        return iter(self.constants)
+
+    def __len__(self):
+        return len(self.constants)
+
+    def __getitem__(self, key):
+        candidate_kdas = set()
+        if key in self.constants:  # Karabo DA name, e.g. 'LPD00'
+            candidate_kdas.add(key)
+
+        for m in self.module_details:
+            if key in (
+                m["module_number"],
+                m["virtual_device_name"],
+                m["physical_name"],
+            ) and m['karabo_da'] in self.constants:
+                candidate_kdas.add([m["karabo_da"]])
+
+        if not candidate_kdas:
+            raise KeyError(key)
+        elif len(candidate_kdas) > 1:
+            raise KeyError(f"Ambiguous key: {key} matched {candidate_kdas}")
+
+        return self.constants[candidate_kdas.pop()]
 
     def select_modules(
         self, module_nums=None, *, aggregator_names=None, qm_names=None
@@ -544,7 +577,7 @@ class CalibrationData(Mapping):
 
     def __getitem__(self, key) -> MultiModuleConstant:
         return MultiModuleConstant(
-            self.constant_groups[key], self.module_details, self.detector_name
+            self.constant_groups[key], self.module_details, self.detector_name, key
         )
 
     def __iter__(self):