Petit Bleu - Paris pneumatic tube message

This is a replica of a "petit bleu" ("little blue"), which were small letters sent via the pneumatic tubes system in Paris, in the 19th and early 20th centuries.
On the front are some instructions for the sender, making clear to where the letter can be sent (only inside Paris), and the address of the recipient.

On the back are additional instructions, telling the sender not to write on the outside of the letter, and not to put any papers or other object inside the letter.
The sender would glue the front and back together around the margins, and the letter would be rolled, inserted into a pneumatic carrier cylinder, and sent on its way through the tube system.

petit_bleu_3jpgTo open the letter, the receiver would tear it open on three sides to reveal the message.