Great and funny postmark! I wondered if it is an official USPS cancelation stamp, but I do think it is!?!
Hi, Heleen. It is official, as these temporary cancellations have to have permission. Any time you see the abbreviation 'stn' (for station) it means a temporary postal station. Usually they are only active for 30-60 days.
Thanks for answering, FinnBadger!
A small correction - the abbreviation for station is 'sta'.
Let me know your thoughts. All your comments are very welcome!