gh-734.js

var mongo = require('mongodb')
pure = require('mongodb').pure();
native = require('mongodb').native();

mongo.Db.connect('mongodb://localhost/native-gh-749?poolSize=2&safe=true', function (err, db) {
  console.log('connected');

  db.collection('stuff').findOne(function (err, doc) {
    console.log(doc._id instanceof pure.ObjectID); //true
    console.log(doc._id instanceof native.ObjectID); //true
    console.log(doc._id._bsontype); //ObjectID

    db.close();
  })
});