The letter reads:
'Be it known that I, Dwalin, Lord of the Longbeards of the Blue Mountains and Steward of Thorin's Hall, write this on behalf of Name. I fought alongside Name to rescue the Elf-prince Elrohir from an alliance of terrible foes including Skorgrim, Ivar the Blood-hand, and Angmarim warriors.
'Should it be within your power, give Name, some measure of welcome and thanks for all that they have done.
Lord of the Longbeards of the Blue Mountains
Steward of Thorin's Hall
Apparently, Dwalin remembers well the travels you and he had together. Seek out Larnin at Celondim or Bogi Deepdelver to see what this letter will yield.
Your assistance with Dwalin against the foes, Ivar the Blood-hand, Skorgrim and the Angmarim has not gone unnoticed. The Lord of the Longbeards sent you a missive which he hopes will bring you favour.
Dwalin, the Lord of the Longbeards, sent you a letter of thanks for your efforts in recovering the Elf Prince, Elrohir, two years ago. His hope is that this letter will earn you some measure of reward from the Elves of Dwarves.