diff --git a/IPython/html/services/contents/tests/test_manager.py b/IPython/html/services/contents/tests/test_manager.py
index 74f471661..f531742f5 100644
--- a/IPython/html/services/contents/tests/test_manager.py
+++ b/IPython/html/services/contents/tests/test_manager.py
@@ -3,6 +3,7 @@
 from __future__ import print_function
 
 import os
+import time
 
 from tornado.web import HTTPError
 from unittest import TestCase
@@ -156,6 +157,7 @@ class TestContentsManager(TestCase):
 
         full_model = cm.get(path)
         nb = full_model['content']
+        nb['metadata']['counter'] = int(1e6 * time.time())
         self.add_code_cell(nb)
 
         cm.save(full_model, path)
diff --git a/examples/Interactive Widgets/Beat Frequencies.ipynb b/examples/Interactive Widgets/Beat Frequencies.ipynb
index 2ae3228c9..13049a34c 100644
--- a/examples/Interactive Widgets/Beat Frequencies.ipynb	
+++ b/examples/Interactive Widgets/Beat Frequencies.ipynb	
@@ -591,9 +591,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:da6a3d73881e321e5ef406aea3e7d706c9dd405c94675318afde957d292f9cb9"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Interactive Widgets/Exploring Graphs.ipynb b/examples/Interactive Widgets/Exploring Graphs.ipynb
index 05f7c1d5c..74f060d69 100644
--- a/examples/Interactive Widgets/Exploring Graphs.ipynb	
+++ b/examples/Interactive Widgets/Exploring Graphs.ipynb	
@@ -830,9 +830,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:61f24f38b76cb12d46c178eadc5d85d61bd0fc27f959236ea756ef8e1adc2693"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Interactive Widgets/Factoring.ipynb b/examples/Interactive Widgets/Factoring.ipynb
index bf7e96980..ffab0b5db 100644
--- a/examples/Interactive Widgets/Factoring.ipynb	
+++ b/examples/Interactive Widgets/Factoring.ipynb	
@@ -131,9 +131,7 @@
    "source": []
   }
  ],
- "metadata": {
-  "signature": "sha256:5f38c57d9570e4b6f6edf98c38a7bff81cd16365baa11fd40265f1504bfc008c"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Interactive Widgets/Image Browser.ipynb b/examples/Interactive Widgets/Image Browser.ipynb
index 96a800542..8430f80ea 100644
--- a/examples/Interactive Widgets/Image Browser.ipynb	
+++ b/examples/Interactive Widgets/Image Browser.ipynb	
@@ -297,9 +297,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:4e9f4ce8fa9be2e33ffdae399daec11bf3ef63a6f0065b1d59739310ebfe8008"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Interactive Widgets/Image Processing.ipynb b/examples/Interactive Widgets/Image Processing.ipynb
index c6d4669a5..cfa1e1024 100644
--- a/examples/Interactive Widgets/Image Processing.ipynb	
+++ b/examples/Interactive Widgets/Image Processing.ipynb	
@@ -26762,9 +26762,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:d75ab1c53fa3389eeac78ecf8e89beb52871950f296aad25776699b6d6125037"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Interactive Widgets/Lorenz Differential Equations.ipynb b/examples/Interactive Widgets/Lorenz Differential Equations.ipynb
index 41130b099..4fdfac4b5 100644
--- a/examples/Interactive Widgets/Lorenz Differential Equations.ipynb	
+++ b/examples/Interactive Widgets/Lorenz Differential Equations.ipynb	
@@ -13428,9 +13428,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:c6ccfb14927d633933da8b5c0f776a8da756d833654b5a3f8b6121b390ca6424"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Notebook/Connecting with the Qt Console.ipynb b/examples/Notebook/Connecting with the Qt Console.ipynb
index f620bb8bd..c76348b04 100644
--- a/examples/Notebook/Connecting with the Qt Console.ipynb	
+++ b/examples/Notebook/Connecting with the Qt Console.ipynb	
@@ -131,9 +131,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:9a1dd30de04270174c09ef33ca214e5b15ca3721547420087c1563ad557d78e3"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Notebook/Index.ipynb b/examples/Notebook/Index.ipynb
index 44baf4e01..6d47cd5b6 100644
--- a/examples/Notebook/Index.ipynb
+++ b/examples/Notebook/Index.ipynb
@@ -68,9 +68,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:5a3c5ebae9154e13957e7c9d28bd3b7697c4b14f965482feb288d2cdf078983e"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Notebook/Running the Notebook Server.ipynb b/examples/Notebook/Running the Notebook Server.ipynb
index 38ada9a9b..2a29326f7 100644
--- a/examples/Notebook/Running the Notebook Server.ipynb	
+++ b/examples/Notebook/Running the Notebook Server.ipynb	
@@ -355,9 +355,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:ee4b22b4c949fe21b3e5cda24f0916ba59d8c09443f4a897d98b96d4a73ac335"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file
diff --git a/examples/Notebook/Working With Markdown Cells.ipynb b/examples/Notebook/Working With Markdown Cells.ipynb
index d8f3dc6e6..e2dead759 100644
--- a/examples/Notebook/Working With Markdown Cells.ipynb	
+++ b/examples/Notebook/Working With Markdown Cells.ipynb	
@@ -296,9 +296,7 @@
    ]
   }
  ],
- "metadata": {
-  "signature": "sha256:3b7cae0c0936f25e6ccb7acafe310c08a4162a1a7fd66fa9874a52cffa0f64f9"
- },
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 0
 }
\ No newline at end of file