GOLD 18K Unknown Ring

Do you mean the shank is marked 14k and the 'mushroom' tested as 18k?
And green gold, do you mean electrum, or modern green gold with cadmium?
The colour is not green, so I assume you mean electrum, which is a naturally occurring gold and silver alloy, often with other metals, and sometimes called green gold.
Natural electrum was still used in South and Southeast Asia until fairly recently. In the West electrum is still made artificially sometimes.

That is what it looks like to me. It could even have been made from two older pieces, the shank with Renee to Jack inscription could have come from another ring.
It is very puzzling.
The detail on the 'mushroom' looks Asian to me, could be Middle East, or somewhere in the southern half of Asia.
The bar or twig looks like something that could have been done in the Retro period, but not with that ethnic granulated look. The bolts remind me of steampunk.

Ok, a steampunk composition of older bits and pieces. Strangely appealing, don't ask me why.