What does the KR on my 1920s ring mean?

by Laura
(Louisiana USA)

What is the item?
This is a 1920's ish diamond ring. Center stone is about 1.5 carat diamond and each side has 2 kite shaped saphires.

Can you please provide all background information?
It was given to me recently as an engagment ring. I could not get a picture that showed the marking. It appears to be white gold


What are the markings? Inside the band
It says 18KR I know what 18K is but cannot figure out the R.


Where are the markings?
Inside of the band