Unknown hallmark, looks like Medusa?!?

[dean_b]

Unknown hallmark, circle with wavy lines (Medusa maybe), on 925 silver Brooch with genuine amethyst stone.
Looks vintage, I would not say it's antique.

Any idea on hallmark origin???

Thanks
Regards

[dean_b]

Perhaps I should write instead of Medusa that the hallmark drawing associates with Jellyfish ?!?