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.