The Golden Arches is dipping into a pot of gold to mark the 50th anniversary of its Shamrock Shake.

Six days after the nationwide return of the popular, mint-flavored shake, McDonald’s announced Tuesday it is auctioning off a jewel-and-diamond-encrusted 18-karat gold cup, called the Golden Shamrock Shake, with bids starting at $1.

The 10-day eBay auction ends at 5 a.m. EST on March 6 with the proceeds from the winning bid going to support Ronald McDonald House Charities, the fast-food chain said in a news release.

The cup, which has emeralds, white diamonds and yellow diamonds, is worth approximately $90,000 and it took a team of jewelers over 140 hours to make, McDonald's said.

“Tradition calls for a 50th anniversary to be celebrated with gold, so we wanted to create an item that not only represented this milestone, but our delicious Shamrock Shake,” David Tovar, McDonald’s vice president of U.S. communications, said in a statement.

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Golden Shamrock Shake eBay auction

The auction is on the Ronald McDonald House Charities eBay for Charity page, a nonprofit whose mission is to “help families with ill or injured children stay close to the resources they need during difficult times.”

McDonald’s says sales from the seasonal shake helped start the first Ronald McDonald House in 1974 in Philadelphia.

Enter to win a Golden Shamrock Shake

If you don’t have excess green to place a bid, McDonald’s is giving away a second Golden Shamrock Shake through a contest.

To be automatically entered in the sweepstakes, purchase a Shamrock Shake or Oreo Shamrock McFlurry through March 6 using the “Mobile Order & Pay” feature in McDonald’s app. Learn more at www.goldenshamrockshake.com.

The Shamrock Shake returned to restaurants nationwide Feb. 19 and is available for a limited time. The Oreo Shamrock McFlurry is a new addition and a twist on the shake with cookie pieces blended throughout the treat.

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Follow USA TODAY reporter Kelly Tyko on Twitter: @KellyTyko