It stands for Yellow Lustrium, a Jewlers alloy
A maker stamp
The ring is made of silver Elite which is a mix or 76% silver, 10% platinum, and some other metals.
An S inside a gold ring is the maker's stamp. If the ring were not gold and had an S inside it would stand for sterling silver.
never heard of a ring with AUP but AU is the chemical symbol for gold so i world bet is gold percantage aka the carat amount.
The XX stamp on gold means 20 karats.
K-R is the logo of the company who made your ring.
Jostens, the famous high school class ring maker says the elt stamper presents Silver Elite. Breakdown of metals is 74-75% Silver, 10% Platinum, and the rest varying base metals.