From the U.S. Postal Service announcement on October 22, 2019:

This stamp honors champion golfer Arnold Palmer (1929–2016). With drive and charisma, he helped transform a game once seen as a pastime for the elite into a sport enjoyed by the masses. The stamp features James Drake’s action photograph of Palmer at the 1964 United States Open at Congressional Country Club in Bethesda, MD. Art director Antonio Alcalá designed the stamp.

The stamp is being issued Wednesday, March 4, in Orlando, FL, at the Arnold Palmer Invitation golf tournament. Details below.

The Scott catalogue number is 5455.

Additional information will be posted below the line, with the most recent at the top.

Updated February 6th
Here are the first-day cancels for this issue: The Digital Color Postmark for this issue measures 1.84″ x 1.48″ The pictorial postmark measures 2.72″ x 1.21″ The special postmark, for use by local post offices, measures 2.97″ x 1.18″

Updated February 1 from the Postal Bulletin:

On March 4, 2020, in Orlando, FL, the United States Postal Service® will issue the Arnold Palmer stamp (Forever® priced at the First-Class Mail® rate) in one design, in a pressure-sensitive adhesive pane of 20 stamps (Item 475900). The stamp will go on sale nationwide March 4, 2020, and must not be sold or canceled before the first-day-of-issue.

This stamp honors champion golfer Arnold Palmer (1929–2016). With drive and charisma, he helped transform a game once seen as a pastime for the elite into a sport enjoyed by the masses. The stamp art features James Drake’s action photograph of Palmer at the 1964 United States Open at Congressional Country Club in Bethesda, MD. Art director Antonio Alcalá designed the stamp.

Availability to Post Offices: Item 475900, Arnold Palmer (Forever Priced at the First-Class Mail Rate) Pane of 20 Stamps: Automatic push.

There is a special dedication postmark for this issue.

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 – Arnold Palmer 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 July 4, 2020.

Technical Specifications:

Issue: Arnold Palmer Stamp
Item Number: 475900
Denomination & Type of Issue: First-Class Mail Forever
Format: Pane of 20 (1 design)
Series: N/A
Issue Date & City: March 4, 2020, Orlando, FL 32862
Art Director: Antonio Alcalá, Alexandria, VA
Designer: Antonio Alcalá, Alexandria, VA
Typographer: Antonio Alcalá, Alexandria, VA
Existing Photo: James Drake
Modeler: Joseph Sheeran
Manufacturing Process: Offset, Microprint
Printer: Ashton Potter (USA) Ltd. (APU)
Press Type: Muller A76
Stamps per Pane: 20
Print Quantity: 25,000,000 stamps
Paper Type: Nonphosphored Type III, Block Tag
Adhesive Type: Pressure-sensitive
Processed at: Ashton Potter (USA) Ltd. (APU)
Stamp Orientation: Vertical
Image Area (w x h): 0.84 x 1.42 in./21.336 x 36.068 mm
Stamp Size (w x h): 0.98 x 1.56 in./24.892 x 39.624 mm
Pane Size (w x h): 5.92 x 7.5 in./150.368 x 190.5 mm
Press Sheet Size (w x h): 11.84 x 22.75 in./ 300.736 x 577.85 mm
Colors: Black, Cyan, Magenta, Yellow
Plate Size: 240 stamps per revolution
Plate Number: “P” followed by four (4) single digits
Marginal Markings:
Front: Header: Arnold Palmer: Professional Golfer • Plate number in bottom two corners
Back: Plate position diagram (6) • 2 Barcodes (475900) • ©2019 USPS • USPS logo • Promotional text

[press release]
Legendary Golfer Arnold Palmer to be Honored With Stamp at PGA Tour Tournament Event

WHAT: The U.S. Postal Service will dedicate a stamp honoring golfer Arnold Palmer (1929–2016), who rose from humble beginnings to become a champion.

The stamp dedication ceremony at the Arnold Palmer Invitational Presented by Mastercard is open to ticketholders. Limited tickets are available for philatelic media available upon request. News of the stamp is being shared with the hashtag #ArnoldPalmerForever.

For more information, visit usps.com/arnoldpalmer.

WHO: The Honorable Roman Martinez IV, U.S. Postal Service Board of Governors

WHEN: Wednesday, March 4, 2020, at 11:15 a.m. EST

WHERE:
Arnold Palmer Invitational Presented by Mastercard
Bay Hill Club & Lodge
9000 Bay Hill Blvd.
Orlando, FL 32819

Background: The U.S. Postal Service will dedicate a stamp honoring golfer Arnold Palmer (1929–2016), who rose from humble beginnings to become a champion. With drive and charisma, he helped transform a game once seen as a pastime for the elite into a sport enjoyed by the masses.

During a nearly decade-long period beginning in 1958, Palmer led the Professional Golfers’ Association of America (PGA) Tour in yearly money winnings four times; won the Vardon Trophy, awarded to the player with the lowest scoring average, four times; and twice earned PGA Player of the Year honors. In 1964, he won his seventh and final major. The six U.S. Ryder Cup teams of which he was a member won the biennial international competition. He captained the team twice, first as a player in 1963, then in 1975. Overall, Palmer won 62 PGA Tour events, the fifth-most of all time, and 92 tournaments worldwide.

The stamp features James Drake’s action photograph of Palmer at the 1964 U.S. Open at Congressional Country Club in Bethesda, MD. Palmer’s name appears in the top left corner and the words “Forever” and “USA” are printed along the bottom of the left edge.

Art director Antonio Alcalá designed the stamp.

The Arnold Palmer stamp is being issued as a Forever stamp, which will always be equal in value to the current First-Class Mail 1-ounce price.