I assumed it was sent to me through the Postcrossing network, but there's no identifying code listed anywhere on the card. I tried searching for it based on the various clues:
- The sender's signature resembles the name in the salutation, "Philipp," though it's addressed to me.
- The postmark indicates it was sent out on July 29, 2009.
- "Philipp" says he lives in the hometown of Beck's beer, namely, Bremen, Germany.
As it stands, an intriguing and well-written card like this, coming out of the blue, is still a pleasant surprise.
Update: It was indeed through Postcrossing. It was sent to me by someone who joined within the last three weeks, and he simply forgot to put the ID code on the card. Postcrossing features an excellent search program: I typed in everything I knew and, while it couldn't find an instant answer, it did later e-mail me with a successful resolution.