GGG's got stamina ... gotta give him that.
The boxing superstar broke out his favorite pen and ripped out HUNDREDS of signatures on Everlast boxing gloves during a marathon autograph session this week ... and it's all for his richest fans.
We spoke with Life In Motion CEO, Thorsten Meier, who says the gloves are a perk for fans who pony up for the special ringside "platinum package" seats for the September 16 fight with Canelo Alvarez.
It's $7,600 for 1 ticket or $14,000 for 2 -- and each order comes with a glove signed by GGG and Canelo, PLUS a hotel room at the Mandalay Bay, PLUS limo transportation from the airport.
As for GGG, don't worry ... his hands were still solid after all the John Hancock'ing.
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