title: Is BinData a Mongo ObjectId?
body: <p>my team is on MongoDB 2.4.10. The id fields look like this</p>
  
  <pre><code>{ "_id" : BinData(3,"fEkTlzkZw8m4JJx5nB+fkw==")
  </code></pre>
  
  <p>I know the 3 is the BSON subtype and the value is Base64. But is this an ObjectId or not?  I'm being told it's not. What I need is an ObjectId getTimestamp() method.</p>