Foreign Gold Hallmark on Ring- What Country?

by Rogue
(Ohio USA)

Hello! I have a small 14K gold malachite cabachon ring in a very simplistic plain setting. What honest to goodness looked like a tiny dent on the outside back of the band turned out under EXTREME MAGNIFICATION to be a hallmark that looks like a narrow very elongated keystone shape with what appears to be a lyre (musical instrument) with then 585 at the base.

Due to the size a photo is impossible- I've tried. We believe this ring is very old, as the other items aquired with it were. I have searched a number of databases and cannot find this particular mark. And just to help, it doesn't look anything like the Irish harp mark, our lyre? is perfectly symettrical. Thanks for any info!