From the U.S. Postal Service announcement on November 17, 2020:
From the USPS: The new Mystery Message stamp will put your sleuthing skills to the test. Featuring bright colors and interesting shapes, the stamp design is a visual riddle spelling out a message. Each colorful square contains a letter in an interesting pattern. The patterns, though seemingly random, were carefully placed so that when put all together, the message reads, “MORE THAN MEETS THE EYE!” Art director Antonio Alcalá designed the stamp.
Additional information will be posted below the line, with the most recent at the top.
Updated August 2nd:
Here are the Scott catalogue numbers for this issue:
The regular stamp is 5614. The imperforate variety is 5614a.
Updated June 17th:
Here are the postmarks for this issue:
The Digital Color Postmark measures 2.98″ x 1.29″ 
The B&W pictorial postmark measures 2.76″ x 1.21″
Updated June 17th from the Postal Bulletin:
On July 14, 2021, in Washington, DC, the United States Postal Service® will issue the Mystery Message stamp (Forever® priced at the First-Class Mail® rate) in one design, in a pressure-sensitive adhesive (PSA) pane of 20 stamps (Item 480700). This stamp will go on sale nationwide July 14, 2021, and must not be sold or canceled before the first-day-of-issue.
The new Mystery Message stamp is designed to put your sleuthing skills to the test! Featuring bright colors and interesting shapes, the stamp design is a visual riddle spelling out a difficult-to-discern message. Each colorful square contains a letter in an interesting pattern. The patterns, though seemingly random, were carefully placed so that when put all together, the message reads, “More Than Meets the Eye!” The reverse side of the pane provides the solution. Art director Antonio Alcalá designed the stamp.
No automatic distribution.
How to Order the First-Day-of-Issue Postmark:
Customers have 120 days to obtain the first-day-of-issue postmark by mail. They may purchase new stamps at their local Post Office™ or at The Postal Store® website at usps.com/shop. They must affix the stamps to envelopes of their choice, address the envelopes (to themselves or others), and place them in a larger envelope addressed to:
FDOI – Mystery Message Stamp
USPS Stamp Fulfillment Services
8300 NE Underground Drive, Suite 300
Kansas City, MO 64144-9900
After applying the first-day-of-issue postmark, the Postal Service will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. There is a 5-cent charge for each additional postmark over 50. All orders must be postmarked by November 14, 2021.
Technical Specifications:
Issue: Mystery Message Stamp
Item Number: 480700
Denomination & Type of Issue: First-Class Mail Forever
Format: Pane of 20 (1 design)
Series: N/A
Issue Date & City: July 14, 2021, Washington, DC 20066
Art Director: Antonio Alcalá, Alexandria, VA
Designer: Antonio Alcalá, Alexandria, VA
Modeler: Sandra Lane / Michelle Finn
Manufacturing Process: Flexographic, Offset, Microprint
Printer: Banknote Corporation of America
Press Type: Gallus RCS
Stamps per Pane: 20
Print Quantity: 20,000,000 stamps
Paper Type: Phosphor, Block Tag
Adhesive Type: Pressure-sensitive
Colors: Cyan, Magenta, Yellow, Gray PMS Cool Gray 5C
Stamp Orientation: Vertical
Image Area (w x h): 1.085 x 1.085 in. / 27.559 x 27.559 mm
Overall Size (w x h): 1.225 x 1.225 in. / 31.115 x 31.115 mm
Full Pane Size (w x h): 5.8375 x 7.12 in. / 148.272 x 180.848 mm
Press Sheets Size (w x h): 14.24 x 23.35 in. / 361.696 X 593.09 mm
Plate Size: 160 stamps per revolution
Plate Number: “B” followed by four (4) single digits in bottom two corners
Marginal Markings:
Front: Header: Mystery Message • Plate number in bottom two corners
Back: ©2020 USPS • USPS logo • 2 barcodes (480700) • Plate position diagram (8) • Promotional text • “More Than Meets The Eye!”
Updated June 15th:
[press release]
Mystery Message in New Forever Stamps
WHAT: Put your sleuthing skills to the test with the bright colors and interesting shapes of the new Mystery Message Forever stamp. The U.S. Postal Service offers intrigue and excitement for customers with a stamp that needs deciphering to be fully appreciated.
News of the stamps is being shared with the hashtag #MysteryMessageStamps.
WHO: Hon. Robert M. Duncan, governor, U.S. Postal Service Board of Governors
Tamara Christian, president and chief operating officer, International Spy Museum
Rebecca Roberts, program curator, Planet Word Museum
WHEN: Wednesday, July 14, 2021, at 10 a.m. ET
WHERE:
International Spy Museum
700 L’Enfant Plaza SW
Washington, DC 20024
The story behind the stamp will also be featured on the U.S. Postal Service Facebook and Twitter pages, posting at 1 p.m. ET.
BACKGROUND: The new Mystery Message Forever stamp is designed to put your sleuthing skills to the test! Featuring bright colors and interesting shapes, the stamp design is a visual riddle spelling out a difficult-to-discern message. Each colorful square contains a letter in an interesting pattern.
The seemingly random patterns were carefully placed so that when put all together, the message reads (here is a “spoiler alert”): “More Than Meets the Eye!” The reverse side of the pane also provides the solution.
Art director Antonio Alcalá designed the stamp. The Mystery Message stamp is being issued as a Forever stamp. This Forever stamp will always be equal to the current First-Class Mail 1-ounce price.
Postal Products: Customers may purchase stamps and other philatelic products through the Postal Store at usps.com/shopstamps, by calling (844) 737-7826, by mail through USA Philatelic, or at Post Office locations nationwide.
Updated March 17th:
This stamp will be issued July 14th with Washington, DC, as the first-day city. “Why?” is still a mystery.
In a year that already promises to set a new standard for the number of pointless issues, this might be the dregs of the crop. Too many issues, and too many of them are just regrettable, and we don’t even have the full list yet.
Just abuses collectors and won’t make any dent in the bottom line. The USPS could at least go broke with dignity. A stamp should look like a stamp.
Maybe the theme of the entire 2021 U.S. stamp program is a “mystery message?”
Every time I feel that a particular issue is not worthy, it seems to develop a life of its own. In about a year or two, it will probably be worth 8 times its face value. I’m not taking my chances on this one. If I’m wrong, then it gets used for my general postage.
I think this stamp should be guaranteed to win the Linn’s 2021 poll for Least Necessary Commemorative Stamp.
I think it will have some competition!
Is the USPO destined to become more and more like the middle east “DUNE”issues, issuing many many stamps that become worthless? Collectors must dig deeper and deeper into their pockets to keep up. Consider the high number issued in 2020! My father stopped buying full sheets and almost quit the hobby over costs.
Many collectors now collect “selected” issues: topics that interest them, certain varieties (coils, booklet panes) and so on. The good news is that unless you are exhibiting competitively, you can do and collect practically anything you want. I used to collect mint ZIP blocks, using either Minkus or Scott preprinted pages. For one issue, the album page showed a strip of 20 of same-design stamps, because the plate numbers extended into what was normally the ZIP block area. (That is, on the selvage of 9 of the 10 stamps on the edge). I said, “Naaaaaaah!” and mounted a block of 4 ZIP block on that space. I mean, it’s a ZIP Block collection. It’s never going to be worth anything, and its sole purpose was to give me enjoyment.
So, Tim, rather than quit all U.S. issues, be selective. Create your own criteria.
I, too, was about to give up on the hobby simply because of the number of issues and the frivolous “sticker” issues until you gave me sound advice, like you are giving Tim. I was disappointed that I couldn’t continue with used and mint examples of every issue, but started being more selective. May even start a separate collection of my birth year issues, both US and worldwide. For me it’s a hobby not an investment; so why not tailor it to fit the budget?
Every collector has their own budget and reason for collecting ( investment vs. pleasure). I am retired and on social security. In 2020 104 digital stamps were issued My issue is with the committee responsible for deciding the design and subject matter of future stamps to be issued. They would be wise to pay heed to the the collectors desire and wants. The pursuit of philatelic issues contributes considerably to the US postal service bottom line..Additional policies imposed by the USPO such as NOT breaking up full sheets is counter productive to the sales of stamps to collectors. Poor choice of subject matter further prevents collectors from obtaining quality stamps which would be considered collectable.
What do you mean by “digital stamps”? I agree with you about the breaking up full sheets.
As a Cachet Artist I look ahead to get my mind working on what I kind of cachet I would do for each stamp. The cachets I would do for this issue is still a mystery to me.
14 July Wash DC
From USA Philatelic 3rd Quarter USPS# 480706 Press Sheet $88.00 #08 Uncut Press Sheet $88.00
If the people at the USPS wants any pointers as to what kind of stamps that their customers like my suggestion is to look at the Quarterly/ monthly issue of Linns’ . The particular section is where The NEW INTERNATIONAL STAMP issues can be found! Enough said
I’d be interested to know what algorithm, if any, was used to modify the letters into the form they currently have. The two Hs for instance are rendered differently.
I’m guessing the artist just played around until it looked done.