From the U.S. Postal Service announcement on November 17, 2020:
From the USPS: The U.S. Postal Service celebrates the enduring legacy of Western wear with four fun new Forever stamps in a booklet of 20. The stamp art features four graphic illustrations of Western wear staples — a cowboy hat, a cowboy boot with a spur, a Western shirt, and a belt buckle featuring a longhorn head. Each image is framed by elements common to the American West and iconography of the region, including cacti, snakes, roses and stars. Art director Greg Breeding designed the stamps with original art by Ryan Feerer.
These stamps will be issued July 23rd in Abilene, Texas, but no first-day ceremony is planned.
The Scott catalogue numbers for this issue are:
5615 Cowboy hat
5616 Belt buckle
5617 Cowboy boot with spur
5618 Western shirt
a. Block of 4, #5615-5618
b. Convertible booklet pane of 20, 5 each #5615-5618
Additional information will be posted below the line, with the most recent at the top.
Updated June 17th:
Here is the Digital Color Postmark for this issue:
It measures 1.98″ x 1.43″
Updated June 17th from the Postal Bulletin:
On July 23, 2021, in Abilene, TX, the United States Postal Service® will issue the Western Wear stamps (Forever® priced at the First-Class Mail® rate) in four designs, in a pressure-sensitive adhesive (PSA) double-sided booklet of 20 stamps (Item 683300). These stamps will go on sale nationwide July 23, 2021, and must not be sold or canceled before the first-day-of-issue.
The Postal Service™ celebrates the enduring legacy of Western wear with four fun new stamps that feature graphic illustrations of Western wear staples:
- Cowboy boot with a spur,
- Cowboy hat,
- Western shirt, and
- Belt buckle featuring a longhorn head.
A stippling technique, creating images using small dots of color, was used to give the illustrations a worn and gritty feel. Each image is framed by elements common to the 
American West and iconography of the region, including cacti, snakes, roses, and stars. Art director Greg Breeding designed the stamps with original art by Ryan Feerer.
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 – Western Wear Stamps
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 23, 2021.
Technical Specifications:
Issue: Western Wear Stamps
Item Number: 683300
Denomination & Type of Issue: First-Class Mail Forever
Format: Double-sided Booklet of 20 (4 designs)
Series: N/A
Issue Date & City: July 23, 2021, Abilene, TX 79601
Art Director: Greg Breeding, Charlottesville, VA
Designer: Greg Breeding, Charlottesville, VA
Artist: Ryan Feerer, Abilene, TX
Modeler: Joseph Sheeran
Manufacturing Process: Offset
Printer: Offset
Press Type: Muller A76
Stamps per Booklet: 20
Print Quantity: 175,000,000 stamps
Paper Type: Nonphosphored Type III, Block Tag
Adhesive Type: Pressure-sensitive
Stamp Orientation: Vertical
Image Area (w x h): 0.77 x 1.05 in./19.558 x 26.67 mm
Stamp Size (w x h): 0.91 x 1.19 in./23.114 x 30.226 mm
Full Booklet Size (w x h): 5.76 x 2.38 in./146.304 x 60.452 mm
Colors: Cyan, Magenta, Yellow, Black
Plate Size: 880 stamps per revolution
Plate Number: “P” followed by four (4) single digits
Marginal Markings:
Front: Header: “Western Wear” Twenty First-Class Forever Stamps • USPS logo • Plate number in peel strip area • ©2020 USPS in peel strip area • Barcode
Back: Promotional text in peel strip area
