Floyd Mayweather didn't just have diamonds all around his neck for the Gervonta Davis vs. Ryan Garcia fight over the weekend -- he apparently had 'em on his head too ... the boxing legend's jeweler tells TMZ Sports the lid Floyd rocked to the match was so encrusted in gems, it was worth over $1 MILLION!!!
Shuki Diamonds told us out in L.A. this week he spent over a month making the blinged-out cap for Mayweather .