It’s a good thing the 49 cash registers in the back of the USGA’s massive merchandise tent operate at a quiet hum.

Otherwise, the non-stop ka-ching-ing likely would create an undignified racket that would rise above the hushed crowds surrounding focused golfers.

Even before this year’s US Open was halfway through, organizers sounded confident that sales revenues from some 400,000 items would break the all-time high set in 2015.

“This will, in all likelihood, unless something really strange happens, bring us our best merchandise sales we’ve ever had at the US Open — sales are fantastic,” said Mary Lopuszynski, the managing director of US Open merchandising.

The USGA does not divulge dollar figures. But public financial statements for the nonprofit organization report the pre-pandemic total revenues from USGA’s Championship events — the big four are the US men’s and women’s Opens and senior Opens, with the men’s Open the chief revenue driver — reached $45.9 million in 2019 (excluding TV broadcast rights), with championship merchandise sales of $3.18 million.

A few factors likely are behind this year’s strong showing.

Besides the opportunity to make a unique (if last-minute purchase) for Father’s Day — the US Open is always well-timed in this regard — attendees are “excited to be out, which they haven’t been able to do a lot” after roughly two years of being mostly cooped up during the worst of the COVID-19 pandemic, said Lopuszynski.

Even the work-from-home trend is working in the USGA’s favor when it comes to selling its apparel.

“Now that we’re working from home, we’re dressing differently, and of course people like wearing golf apparel but you can also wear it at home, this is regular work apparel now, and that’s shifted a lot from what it used to be,” said Lopuszynski.

Lopuszynski and 10 other USGA merchandise full-time staffers, along with 21 interns, have been on site since May 1, preparing for what amounts to one of the largest pop-up stores you’ll ever find.

Of the tournament’s 3,800 volunteers, 1,100 are deployed for selling merchandise from some 250 different vendors.

The main tent occupies 24,000 square feet on what is normally The Country Club’s driving range, situated conveniently between the first and 18th holes. There’s also an annex tent, occupying some 6,600 square feet near the 14th hole.

The main merchandise tent at past US Opens usually take up 36,000-39,000 square feet, but that wouldn’t work for the relatively small footprint of The Country Club. But the smaller size is in no way slowing down the pace of sales, said Lopuszynski.

Customers are plucking items from shelves and racks quickly, requiring frequent restocking managed via a back-of-house storage facility that features 17 full-size UPS cargo truck containers.

New merchandise is still being shipped in — multiple boxes of Ralph Lauren items were being cataloged Friday afternoon.

With cooler weather in the forecast for Sunday, orders of 5,000 more pieces of outerwear have been placed.

Even Friday’s brief flirtation with downpours, which did not arrive despite the severe weather warnings, plenty of attendees found refuge in the tent.

“We had a pretty good hour,” said Lopuszynski with a laugh.

The biggest seller in the tent is headwear, which comprises roughly 25 percent — about 100,000 hats in all — of merchandise. There’s about 220 kinds of hats — baseball, visors, bucket — with the straw hats already sold out.

The Country Club’s squirrel mascot and yellow-and-green color scheme is proving to be a hit, said Lopuszynski.

“It’s maybe one of the best logos we have and the most popular — people love it, it’s just a little different, a little quirky,” she said.

Besides hats, men’s, women’s and children’s apparel from nine companies take up much of the floor space, along with plenty of golf items, including about 20,000 golf towels and 25,000 ball markers.

Prices range from $2 for ball markers to close to $300 for some men’s jackets.

Besides about 500 straw hats, other items have sold out, such as all the Christmas ornaments, some 280 inflatable bouncy balls used mainly by kids for autographs, about 100 bronze clover ball markers, and around 1,500 small stuffed squirrels.

“Boston is a great sports town,” said Lopuszynski. “But now having the US Open come here after so many years, I think the excitement level was off the charts, so that’s cool. It’s always nice to be somewhere where people think this is as special as we think it is.”

Michael Silverman can be reached at michael.silverman@globe.com. Follow him on Twitter: @MikeSilvermanBB.

Work at Boston Globe Media