It's actually a coin, a krugerrand from South Africa. And it's pure gold, unlike the medal Justin Rose won in Rio de Janeiro at the Olympics. A friend gave it to him, and Johnson was using it Wednesday during his pro-am at the BMW Championship.
Johnson is aiming for something more valuable, at least in terms of cash.
He is No. 3 in the FedEx Cup going into the third playoff event, and the U.S. Open champion is virtually assured of being among the top five who would only have to win the Tour Championship to capture the $10 million bonus.
The FedEx Cup is at the halfway point, and it's starting to feel like a sprint -- perhaps it felt like a slowdown for several players who stopped by the Indianapolis Motor Speedway on Tuesday to drive BMWs around the track.
Patrick Reed is No. 1 in the standings based on his victory at The Barclays and a tie for fifth at the Deutsche Bank Championship. He's followed by world No. 1 Jason Day, Johnson, Deutsche Bank winner Rory McIlroy and Adam Scott.
THE THIRD LEG: Only 70 players advanced to the BMW Championship, the final stop before the top 30 reach the Tour Championship.
Jordan Spieth is at No. 6 and eager to move into the top five, for those are the players who control their own Buy Krugerrands fate in two weeks at the Tour Championship. The first step is to get there, and it would appear that no more than eight players have a chance to move into the top 30.
Kevin Na dropped from No. 14 to No. 23 because he skipped last week when his wife gave birth. Henrik Stenson is No. 24, and his prospects are tenuous because the British Open champ is not playing Crooked Stick to rest his right knee and his mind for the Ryder Cup.
Bubba Watson narrowly missed out on qualifying for the Ryder Cup. He is at No. 27 and is hopeful he doesn't narrowly miss out on East Lake.
Just outside the top 30 is Daniel Berger, the only PGA Tour rookie last year to make it to the Tour Championship.
CROOKED STICK: John Daly was the ninth alternate when he introduced the world to his "grip it and rip it" ways in the 1991 PGA Championship, and that explains a lot about this Pete Dye design just north of Indianapolis.
It's a big course, and it's tailored for big hitters.
McIlroy made bogey on the last hole in 2012 and still won by two shots at Crooked Stick over a cast of contenders that included Lee Westwood, Phil Mickelson, Tiger Woods, Dustin Johnson and Adam Scott.
RYDER CUP: As usual, the FedEx Cup shares the billing with the Ryder Cup at the playoff events this year. U.S. captain Davis Love III makes three of his four picks on Monday after the BMW Championship.
Even though Mickelson says the initial three picks "are fairly obvious," the list of candidates goes from Rickie Fowler and Matt Kuchar to Watson and J.B. Holmes, and perhaps a younger player who has had a solid year and wins the BMW Championship.
A good week wouldn't hurt an American's chances.
AWARD RACES: Johnson and Day are locked in a tight battle as front-runners for PGA Tour player of the year with only two tournaments remaining before the players vote.
But there's more.
The top five in the running for the Vardon Trophy -- a prestigious award for the lowest adjusted scoring average -- are Day, Johnson, Mickelson, Spieth and Scott. Day at No. 1 and Scott at No. 5 are separated a 0.273 average, so it's still anyone's game.
One other race is for PGA Tour rookie of the year. The tour declared Si Woo Kim a rookie. The South Korean won the Wyndham Championship three weeks ago and is No. 18 in the FedEx Cup, making him a lock for East Lake. Emiliano Grillo, who won the first tournament of the season and contended in the PGA Championship on Sunday, is No. 8 and the leading rookies. Smylie Kaufman won in Las Vegas, played in the final group at the Masters and is No. 33, needing to get into the top 30 to have any chance.