Amazing gesture fromDak Prescott ... the Dallas Cowboys QB gifted his older bro with an incredible diamond moose pendant to remember their late brother -- and TMZ Sports has learned it was all super emotional.
We're told in mid-November, Dak hit up Paul Mazza at Mazza New York to try to get a birthday gift made for Tad Prescott -- Dak's older bro -- in time for his Nov. 25 celebration.
Mazza tells us he and Dak got to talking about possible jewelry pieces for the occasion ... when the 27-year-old NFL star had the idea to commission a diamond moose pendant.
Dak and Tad's other brother, Jace Prescott, was nicknamed "Moose" before he tragically died by suicide last April -- so the QB felt it would be special for Tad.
Knowing the importance of such a gift for the Prescotts ... Mazza says he got to work on crafting a masterpiece ASAP -- and was able to deliver an unbelievable pendant in less than 2 weeks.
Mazza New York
Mazza tells us the bling features 65 grams of 14k white gold and 9.5 carats of VVS E through D diamonds that were all hand-set on the antlers in a flower setting.
Mazza says the whole thing was also hand-painted in a jewelry enamel ... and features the words "In Memory of Jace 'Moose' Prescott" on the back.
And, when the Prescotts received the gift ... Mazza tells us Tad was so moved by the creation -- he broke down in tears.
"Dak sent me a personal video thanking me," Mazza said. "He said, 'You made somebody's birthday.'"