Just got an old 787 improved muskrat from my grandfather who just passed away. This thing looks old, blades sharpened so much they are missing some metal. Any idea how old this knife is. It has Scherade Walden NY USA on one side of the long blade and 787 on the other side. Looks like SS caps on the ends. The sheild says Improved Muskrat. Other than sentimental value, is this worth anything? Thanks for any info.