Jigsaw greeting card. Write your message on the back of the jigsaw card, break the pieces apart, put them in the envelope and send it away as a regular letter (weight under 20 grams). The receiver must put the pieces together before he/she can read the message.
"That was so FAST. Excellent efficiency, you have "Wow". I paid yesterday & it showed up today at 11.15am. I am so pleased with everything you have done for me." Celeste, Auckland