US mail. No Box. Your name address and phone number taped to the inside of the case in a easy to see location. In addition to the mailing label.
Do you have a place to mail it to.? Some Post offices hold packages in general delivery. C/O general delivery
might hold it for 30 days. Call the post office in question to be sure.
An s&s case can be carry on luggage for Amtrak. I use a cable lock to secure mine to the luggage rack.