It means that the ring was hallmarked in Birmingham, UK You can see more detail here http://www.gold-traders.co.uk/news/2008/01/simple-gold-hallmark-guide.html
Palladium
It means that the ring is made of 18K gold.
it means it is 18 carat gold ring or 76% pure gold
The Stamp YAG Means Gold Coated Silver
That's a manufacturer stamp
Not
silver
the stamp shows that the ring is of 14 karat gold piece; to check if it is real or not.
What does SW mean in a horseshoe gold ring
375 is 9k gold.
gold metal crap
FAS 925 on a gold ring what does it mean?