Thank you for the excellent details - that helps a lot!
What you have described sounds like a *genuine vintage 18k estate set.*
*1. The 18K Mark:* 18K means 18 karat, which is 75% pure gold. In Europe it is marked as *750*. This is the fineness mark and it confirms the gold content. That is your main value mark.
*2. The "Wavy Line and Dot" Mark:* This is the important one. Beside a fineness mark, you almost always get a *Maker's Mark or Sponsor's Mark.*
A wavy line with a dot is _not_ a standard government assay mark. It is almost certainly the jeweler's signature logo, stamped on the back of the cufflinks and inside the ring band - exactly where a maker would put it.
There are two very common makers who use a wavy / squiggle mark:
- *If it looks like ~ with a dot* - It is often an Italian maker. Italy uses 750 and a _star + number + province code_ but older Italian pieces also used abstract logos like a wavy line. - If it is a very fine, tiny wavy line - It can also be a British or American designer signature mark from the 1950s-1970s, when abstract logo marks were fashionable for matching men's sets.
Because it is on both the cufflinks and the ring, it confirms they are a *true original matching set*, not married together later. That adds value.
What to do next to identify it:
Could you possibly add one extra detail for me?
- Is the wavy line inside a shape? Like a diamond, oval, or shield? - Can you see any numbers next to the wavy line?
Clean or polish with care. The patina and the soft edges of those marks are part of the proof it is antique estate jewelry from inheritance.
It sounds like you have a lovely heirloom set - these matching cufflink + ring sets were very popular for grooms in the mid-century and are highly collectible now because most sets have been split up.
