It was sent US Postal Service priority mail, received by a postal clerk. The postmark has a timestamp.
Did a postal clerk take it from him personally during that two hour time frame, or had he put it in the mailbox, where the workers picked it up, time stamped it, then sent it on? Every post office has those Express Mail envelopes out there for anyone to take and use. Does that particular post office location have security cameras that show customers at the counter?