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"