Daniel Webster signed note to the Revere House

This note/letter was found when the owners of Daniel Webster's farm land was sold by the Sisters of Holy Cross. The note is signed and dated on April 28, 1851. The letter was thanking them for a pen he had acquired from them and telling them that it was "quite beautiful" and that he was writing that note with it and that "it is in truth, the only metalles pen he had ever been able to use".
It's quite nice and in really good condition.....I would like know what the estimated value may be on it....Thank you in advance for your help.