An Autographed Card Sold for $4.6 Million. Did Luka Doncic Really Sign It?

Collectors who agree that the “Lulu” signatures are legitimate point to a gift for the Slovenian president that features one, a skipped pen stroke that has been observed in both archetypes of autographs, and the fact that grading companies authenticate them.

A spokeswoman for Beckett Grading Services said in an email that outside speculation about Doncic signatures did not influence its autograph experts, who consider “the letter shape and formation, the pen pressure, the flow, rhythm, conviction and spontaneity of the signature, and letter size and spacing to determine if it is consistent with known exemplars.” Professional Sports Authenticator declined to comment.

Another common defense of the “Lulu” signatures is that the variations can be attributed to fatigue from frequent signings. Industry experts said that it took about an hour to sign 400 stickers and that Doncic might have signed at least 10,000 as a rookie.

Gellman, who runs Sports Cards Uncensored, dismissed that explanation, noting that he once watched the quarterback Johnny Manziel replicate his intricate signature for four hours.

“Athletes are required to sit and do this for so many parts of their life that it becomes secondhand to sign everything the same,” Gellman said.

Ultimately, the rumblings about Doncic’s signature have not dulled the top end of his card market.

Nick Fiorella, an entrepreneur who puts most of his disposable income into sports cards, said his riskiest purchase was the $4.6 million Doncic card with an N.B.A. logo and a “Lulu” autograph. But he is betting that the player and the hobby will continue to soar.

“To me, if it’s him or his mom or whatever, it’s always going to be his one-of-one,” Fiorella said. “If he becomes a transcendent player, it doesn’t really matter if I signed it.”

Sheelagh McNeill contributed research.