This is the green glass skull shot from a red and green matched set freely mailed out to friends of Tiki Farm for Christmas 2020, and later sold on their site as well.
From Tiki Farm:
"Season’s Greetings with a Red and Green Skull Shot Set with the Tiki Farm black logo on the back.
Cheers to a brand New Year and cheers to many new mugs on the horizon!
Original release year: 2020
Capacity: 2 oz. each shot
Height: 2 3/8 inches"