diff --git a/caravel/controllers/listings.py b/caravel/controllers/listings.py
index 52d1451..5b58c4b 100644
--- a/caravel/controllers/listings.py
+++ b/caravel/controllers/listings.py
@@ -67,7 +67,8 @@ def inject_globals():
     """Adds the categories and user info into the view."""
     return {'categories_list': model.Listing.CATEGORIES_LIST,
             'categories_dict': model.Listing.CATEGORIES_DICT,
-            'current_user': users.get_current_user()}
+            'current_user': users.get_current_user(),
+            'is_admin': users.is_current_user_admin()}
 
 # Display the time as "1s" etc.
 @app.template_filter("as_duration")
diff --git a/caravel/templates/listings/fullpage.html b/caravel/templates/listings/fullpage.html
index 8cbf3e5..5a5ccf6 100644
--- a/caravel/templates/listings/fullpage.html
+++ b/caravel/templates/listings/fullpage.html
@@ -32,6 +32,13 @@ <h2>{{ listing.title }}</h2>
           {%- endif -%}.
           Price: <strong>{{ '${:,.2f}'.format(listing.price) }}</strong>
       </p>
+      {% if is_admin %}
+      <p class="alert alert-info">
+        {{ listing.principal.explain() }}. Originally posted by
+        {{ listing.principal.device.ip_address }} with 
+        {{ listing.principal.device.user_agent }}. 
+      </p>
+      {% endif %}
       <p style="white-space:pre-wrap">{{ listing.body }}</p>
     </div>
     {% if not is_from_tor() %}
diff --git a/caravel/tests/test_listings.py b/caravel/tests/test_listings.py
index 23a645a..bcca058 100644
--- a/caravel/tests/test_listings.py
+++ b/caravel/tests/test_listings.py
@@ -121,7 +121,8 @@ def test_post_inquiry_with_cnetid(self):
                 "New Listing Logged in as visitor@uchicago.edu My Listings "
                 "Logout Your inquiry has been sent. Listing \xe2\x98\x86B "
                 "apartments Posted 2d ago by seller-b@uchicago.edu . Price: "
-                "$71.10 Body of \xe2\x98\x86B Contact Seller From "
+                "$71.10 Validated by GOOGLE_APPS. Originally posted by 1.2.3.4 "
+                "with mozilla. Body of \xe2\x98\x86B Contact Seller From "
                 "visitor@uchicago.edu ( Logout ) Message")
 
         # Verify that the proper email was sent.
@@ -239,6 +240,7 @@ def test_new_listing_with_cnetid(self):
                 "New Listing Logged in as visitor@uchicago.edu My Listings "
                 "Logout Your listing has been created. Title of \xe2\x98\x86D "
                 "apartments Posted now by visitor@uchicago.edu . Price: $3.44 "
+                "Validated by GOOGLE_APPS. Originally posted by None with . "
                 "Body of \xe2\x98\x86D Manage Listing Edit")
 
         # Make sure the picture shows up.
@@ -334,7 +336,8 @@ def test_edit_listing(self):
             self.assertEqual(self.clean(self.get("/listing_a").data),
                 "New Listing Logged in as seller-a@uchicago.edu My Listings "
                 "Logout Your listing has been updated. Title\xe2\x98\x86A cars "
-                "Posted now by seller-a@uchicago.edu . Price: $2.34 "
+                "Posted now by seller-a@uchicago.edu . Price: $2.34 Validated "
+                "by GOOGLE_APPS. Originally posted by None with . "
                 "Body\xe2\x98\x86A Manage Listing Edit"
             )
 
diff --git a/caravel/utils/principals.py b/caravel/utils/principals.py
index c815516..3ce47fd 100644
--- a/caravel/utils/principals.py
+++ b/caravel/utils/principals.py
@@ -1,4 +1,5 @@
 import uuid
+import user_agents
 
 class Device(object):
     @classmethod
@@ -51,6 +52,16 @@ def validate(self, reason):
 
         self.validated_by = reason
 
+    def explain(self):
+        """
+        Return a string explaining why this Principal is valid or not.
+        """
+
+        if self.auth_method in (self.GOOGLE_APPS, self.LEGACY):
+            return "Validated by {}".format(self.auth_method)
+        else:
+            return self.validated_by 
+
     def __repr__(self):
         """
         Returns a readable representation of this Principal.