The post office in Spokane, Washington had an interesting problem. On December 18, 1955, someone dropped off fifty envelopes to be mailed. All were properly addressed and stamped, but lacked one important piece: All of the envelopes were completely empty.
Apparently the mailer had forgotten to insert the Christmas cards or whatever they had intended to include. There was no return address on any of the envelopes to help identify the sender and while you are about 63-years too late, should you know what should have gone into those envelopes, please be sure to contact the Spokane post office.