Possible to resize ring from 15.5 mm to 18 mm..?

[acaw2015]

Hi!
I have my eyes on a (possibly Edwardian with old cuts) ring. But what do you think, is it possible to have a ring sized 15.5 mm resized to 18 mm..? No pave on the shank, platinum.
Many thanks!

 

[rockysalamander]

Probably, but it will depend on the shoulder details and structure of the ring. It will take a skilled bench jeweler. They will cut the bottom, insert a piece and the join that into the ring. Look for someone who can LASER WELD over solder. You will lose the antique look on the ring, as they need to re-finish (shape and polish). On platinum, I prefer to have them apply a matte or light satin finish. It takes that high-shine off and makes it look more vintage faster. It will soften to more shiny over time.

Real vintage rings of that era (assuming it is not a replica) like need other restoration work...repair, re-tiip prongs, reapply milgrain or other historic texture, fix or renew engraving. Be prepared that it may be more expensive that simply getting the re-sizing done.

 

[acaw2015]

Amazing answer, thank you @rockysalamander
You are right re everything. There are shoulder details, millegrain etc. I should probably discuss the ring with an experienced jeweller before proceeding...