296
A Roman “hologram” effect ring found in the grave of 1st century AD noblewoman, Aebutia Quarta.
(lemmy.world)
The ring is thought to depict her son, Titus Carvilius Gemello, who passed away at age of 18. Found at the Grottaferrata necropolis close to Rome.
I can't be sure, but this appears to be the Hollow-Face optical illusion. It would be achievable with this technology as well
Hollow face illusion produces a face that appears to follow the observer. This just looks like a sculpt under glass.
That's kinda what I assume, in practice - a negative relief carved into the back of amber or what have you.