5/8"
I have no idea who made this. Came in the Advent gift box. My first thought was Alley. Then Ravenswood. Then I wondered if Akro was a possibility.
First two views sunlight. Next with flash. Then UV. I guess the pictures are pretty close, except there is more distinct clarity in the base glass, with what I am seeing as tan filaments. (But I couldn't tell 100% if it was tan filaments in clear or white filaments in a tinted base.)