It is unusual in that to accept the pass for time away, the soldier first had to sign an oath of allegiance to the United States. That seems sort of unnecessarily as if the soldier had any intention of not coming back and deserting, would he really care what he signed? The oath is an integral part however for captured Confederates who were allowed to go home if they signed such a document and said they would not take up arms again against the Union. But then whatever a human being signs probably doesn't affect what he or she does.
Very interesting and rare document.