Abraham Lincoln Signature

I have a land deed signed by Abe Lincoln. Short story, I had a family member that some how worked for a national agency or such. My ancestor did work for the Indians. Since the Indians didn't have money, they paid him in land. So I have a land deed from the Indian land management that was signed by Abraham Lincoln with a date of I believe 3/8/1862.

My fathers' family is from WA State for which this land was given. Washington state museums have been asking for this piece as well as 3 others just like it signed by Ulysses S Grant. Everything is in excellent shape besides the folds in the paper. Everything is legible and readable, with no faded signatures. I was wondering how much it might be worth and where would I be able to take this document. I live in Chino, CA.

Thank you for your help,
Jason Case