diff --git a/include/boost/detail/identifier.hpp b/include/boost/detail/identifier.hpp
new file mode 100644
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+++ b/include/boost/detail/identifier.hpp
@@ -0,0 +1,87 @@
+//  boost/identifier.hpp  ----------------------------------------------------//
+
+//  Copyright Beman Dawes 2006
+
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  See documentation at http://www.boost.org/libs/utility
+
+#ifndef BOOST_IDENTIFIER_HPP
+#define BOOST_IDENTIFIER_HPP
+
+#include <boost/utility/enable_if.hpp>
+#include <boost/type_traits/is_base_of.hpp>
+#include <iosfwd>
+
+namespace boost
+{
+  namespace detail
+  {
+    //  class template identifier  ---------------------------------------------//
+
+    //  Always used as a base class so that different instantiations result in
+    //  different class types even if instantiated with the same value type T.
+
+    //  Expected usage is that T is often an integer type, best passed by
+    //  value. There is no reason why T can't be a possibly larger class such as
+    //  std::string, best passed by const reference.
+
+    //  This implementation uses pass by value, based on expected common uses.
+
+    template <typename T, typename D>
+    class identifier
+    {
+    public:
+      typedef T value_type;
+
+      const value_type value() const           { return m_value; }
+      void  assign( value_type v )             { m_value = v; }
+
+      bool operator==( const D & rhs ) const   { return m_value == rhs.m_value; }
+      bool operator!=( const D & rhs ) const   { return m_value != rhs.m_value; }
+      bool operator< ( const D & rhs ) const   { return m_value <  rhs.m_value; }
+      bool operator<=( const D & rhs ) const   { return m_value <= rhs.m_value; }
+      bool operator> ( const D & rhs ) const   { return m_value >  rhs.m_value; }
+      bool operator>=( const D & rhs ) const   { return m_value >= rhs.m_value; }
+
+      typedef void (*unspecified_bool_type)(D); // without the D, unspecified_bool_type 
+      static void unspecified_bool_true(D){}    // conversion allows relational operators
+                                                // between different identifier types
+
+      operator unspecified_bool_type() const   { return m_value == value_type() ? 0 : unspecified_bool_true; }
+      bool operator!() const                   { return m_value == value_type(); }
+
+    // constructors are protected so that class can only be used as a base class
+    protected:
+      identifier()                             {}
+      explicit identifier( value_type v )      : m_value(v) {}
+
+    private:
+      T m_value;
+    };
+
+  //#ifndef BOOST_NO_SFINAE
+
+  //  template <class Ostream, class Id>
+  //    typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, 
+  //      Ostream & >::type operator<<( Ostream & os, const Id & id )
+  //  {
+  //    return os << id.value();
+  //  }
+
+  //  template <class Istream, class Id>
+  //    typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, 
+  //      Istream & >::type operator>>( Istream & is, Id & id )
+  //  {
+  //    typename Id::value_type v;
+  //    is >> v;
+  //    id.value( v );
+  //    return is;
+  //  }
+  //#endif
+
+  } // namespace detail
+} // namespace boost
+
+#endif // BOOST_IDENTIFIER_HPP