I bought a small collection of these glasses a while back from Belgium.
They're thin-walled, very lightweight, 80mm / 3 1/8" tall, with a fine vertical optic rib pattern throughout, a thicker moulded foot, a moulded base, and a fire-polished rim. Yellow-green under standard light, strong green under UV.
They have a 1930s-50s feel about them, but are possibly a little earlier. I would assume that they're for fortified wines or liqueurs.
Any help gratefully received.