Featured Help identifying a rosecut ring- foil-backed?

I sold a couple of rings for a friend. They'd been made from rather splendid diamond cluster earrings, so that two sisters could each inherit.

 

Just to add a couple of interesting tidbits: During WW2, in Italy, a U.S Army priest let it be known that he was interested in old coins. Occasionally a GI would bring him a coin that he had found in a shell hole or where ever. One coin was Roman and was chipped, exposing a center which was of a different metal. After the war the coin was found to have a center of Platinum with an exterior of silver....a counterfeit coin with a worthless center. Another item of interest is that in Ore., U.S. after the 1849 gold rush, placer miners discarded a white metal from their collection weirs because it was worthless. It is now thought that that white metal was platinum

 

Wow thank you so much for all of your responses! I hadn't gotten any notifications so I had assumed that the thread was dead. To be completely honest what I know about it is just what I have been told. The ring does have some hallmarks but I am a complete newbie and have not been able to properly identify any of them. I will post a photo here but since it's not a great photo here is what I was able to see from looking at the ring closely(from left): JAP, not sure, not sure, 18k, R8. I have seen many rings from the Georgian era with similar gold band, silver setting but I think that this ring must be inspired by that time/a recreation from around 1940-1960? Again not sure. Really appreciate all of the responses! https://ibb.co/TrwSbRG
Also, I am now 99% certain that the diamond is foil-backed and am wondering if anybody has experience with foil-backed jewelry. Mostly what I want to know, is what it might look like with moisture damage. I think maybe coppery if the silver foil gets wet?

 

Looks like Swedish hallmarks, R8 ist the mark for 1943

Town mark for Stockholm, Makers Mark for Persson J. A., 100 01 Stockholm (used from 1932 - 1948)

 

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Thanks for taking a look. I never click on links, unless it is really clear to me what it is.

 

Wow thank you so much!!! I think you may be right! I found this page which has the date letters and a very similar stamp.

http://www.silvercollection.it/DICTIONARYEUHALLMARKSWEDEN.HTML