Featured Hidden Gem Next to Jewler's Mark?!

I found this earring near a garbage bin. I had a friend who worked in the jewelry business for a few years and said it was worthless costume jewelry. She said there was mounting screws visible inside the earring. However, upon close examination with my camera, I discovered those "screws" were in-fact a jeweler's mark and the most unique thing I've ever seen... an inside mounted gemstone (assuming a diamond) next to the mark. Any ideas what make this is?! I'm guessing that's either an "Z" or a "N. Based on the serifs, I'm guessing a "Z". The "gems" don't seem that sparkly. Seems a little elaborate for costume jewelry.

Any advice / help would be appreciated!



PS> Now that I see the photos up-close, it appears the gold has pink tarnish on it?!

 

It looks like copper under the worn plating. Usually glued in (outside) stones are not precious. The inside one may be just so they can legally say diamond in its description.

 

nice pics..........Terry may be on the right track !

 

The photos are out of focus to see anything pointing what exactly it is.

 

Sneaky! Everything you pointed out makes sense!

 

could it be like an "extra" the way they give an extra button with dress shirts in case one of the stones falls out? just a silly and unlikely guess! Looks like an N to me, I feel like for a Z, the length of the parallel lines would be less wide and farther away from eachother so the diagonal line is longer- Again, just a total guess!!

 

I think that's a Napier costume mark.

 

I don't think it is Napier, because Napier's mark is inside an oval, not a circle. But it looks like gold wash over copper, and the inner jewel is an extra in case one falls out on the pave' set rhinestones. I think they would be worth a little, especially if you could find maker. May be European.