He was brash, not afraid to flash stacks of cash, and was a wizard at finding a valuable sports card stash.

Alan "Mr. Mint" Rosen, a self-promoting dealer who in turn gave massive publicity to the sports card and memorabilia hobbies, died early Thursday, Sports Collectors Digest and Beckett Media reported. He was 70 and had been battling leukemia for several years.

Before there were auction houses, Rosen would travel the country during the 1980s and ’90s with an attaché case stuffed with $100 bills, ready to make a deal for high-end vintage cards or entire collections. He took out full-page advertising in collectibles trade magazines and billed himself as "The world’s largest buyer of baseball cards and sports cards." At card shows, he demanded — and was granted — a booth near the front door.

In a July 4, 1988, feature, Sports Illustrated writer Dan Geringer called Rosen "the King of Cards, the Duke of Dough" in the high-stakes baseball card game.

"Deals are Mr. Mint’s lifeblood," Geringer wrote. "Sentiment is Mr. Mint’s blood poisoning."

In a 1990 interview with the Los Angeles Times, Rosen was asked what he personally collected.

"I collect money," he said. "Hundred-dollar bills. I’m loud, I’m a braggart and I’m brash. But I’m the best.”

Rosen was not afraid to tout his discoveries. His website was full of them, but all were impressive. In 1986, he uncovered the "1952 Topps Find" in the Boston area, which included more than 6,000 gem mint high numbers — including 65 Mickey Mantle cards. He also uncovered a stash of 500 unopened 1954 and 1955 Topps and Bowman baseball cards in Paris, Tennessee.

Rosen also bought nine of the iconic Honus Wagner T-206 tobacco, known to collectors as the Holy Grail of baseball cards.

In an interview with Beckett Media, Steve Grad, of the Dallas-based collectibles company’s Authentication Services division, called Rosen "a pretty interesting guy."

"He’d seen just about everything in our business. He’d been all over buying stuff and he had a pretty cool perspective," Grad said. "Did he know everything? No way. He wasn’t really good with autographs and authenticity, or if a card had been altered, but he knew how to buy collections."{

Rosen authored several books. In 1991, he and Doug Carr co-wrote Mr. Mint's Insider's Guide to Investing in Baseball Cards and Collectibles. Three years later, he teamed with T.S. O'Connell to write True Mint: Mr. Mint's Price & Investment Guide to True Mint Baseball Cards.

Before finding his niche as a collectibles dealer, Rosen sold insurance, jewelry and clothes. The idea of selling cards came to him in 1978 as he wandered through a card show in his hometown of Paterson, New Jersey. In 1982, he gave up a copy machine and antique business in New Jersey and began buying and selling sports cards on a full-time basis.

Stories about Rosen are plentiful. Love him or hate him, collectors had stories to tell about Mr. Mint.

Tom McDonough, who runs the annual Cranston Sports Collectors Show in Rhode Island, said Rosen was “a show within a show” when he appeared at sports memorabilia shows.

McDonough told Sports Collectors Daily in 2016 that Rosen would fly into the area the night before the show and they would have dinner together. One year, McDonough said, Rosen entered the restaurant "wearing a long trench coat and carrying an attaché case."

"I’m prepared to spend $100,000 tomorrow," Rosen said. "Have you ever seen $100,000?"

Rosen snapped open his attaché case to reveal $100,000 in hundred-dollar bills. McDonough gasped, and then wondered why Rosen would walk around with so much cash.

"I told him that people get jumped for 10 bucks," McDonough said. "Then he pulled back his coat, and he had a gun."

The 2008 movie "Diminished Capacity" spoofed Rosen with a character called "The Mint-Mint Man," played by Bobby Cannavale. In the film, "The Mint-Man" fleeces Uncle Rollie Zerbs (Alan Alda), buying an extremely valuable baseball card for just $500. Predictably, Rosen was not amused, according to a story that ran in Sports Collectors Digest.

Despite his reputation for abrasiveness, Rosen would help fledgling collectors. Vintage card collector T.J. Valacak recalled an assist from Mr. Mint during a 1999 collectibles show in Chicago.

“Bobby Thomson was signing autographs. As a diehard Red Sox fan, I wanted to get an autograph of Thomson on a Red Sox card,” Valacak said. “I went to a few tables. As you can imagine, for someone getting back into the hobby, there were thousands of cards at each table and I was overwhelmed.

“I was familiar with who Mr. Mint was, and I had recognized him when I walked in the show.  So, I ventured to his table and asked him if Bobby Thomson had ever appeared on a baseball card as a Red Sox player.  Immediately, he told me 1960 and told me a range of numbers.”

Impressed, Valacak was able to find the Thomson card he wanted and got the hero of “The Shot Heard ’Round the World” to sign it. Rosen’s assistance also rekindled Valacak’s love for vintage cards. After getting Thomson’s autograph, Valacak bought “about 300” commons from the 1972 Topps set.

“I was back in,” he said. “So, when I think about my vintage collection and when I got back in the hobby, my brief conversation with Mr. Mint always flashes in my mind.  I was so impressed with his knowledge that day.

"The next few times I would go to the semiannual Chicago show, I would stop by his table and talk about one of his auctions.  He was always pleasant with me."