Definitely not a Grumly. The Bear logo ont he bow was not used 'til long after Nels was gone from Bear, I don't think he ever made a "CUB", and the style of the limbs and tips are definitely not his.
Although I am not that familiar with Nels' signature, I have seen enough of Fred's signatures to guess that this is not his,
Can your spell F-R-A-U-D