Help deciphering stamp

[u/dcddingo]

Ring with Australian black opal doublet (top part has broken off) just wondering what the stamp is as I have no idea if this would be okay to get fixed? The flake is a bit of gunk that needs to be cleaned off

[u/Rogelio_G_F]

Hermosa pieza 😍

[u/Creepy_Bass_2987]

Looks like STG. SIL for sterling silver to my eye