Consists only of his handwritten Hopi dictionary.
It appears that some, maybe most, of the handwriting in this volume is H. R. Voth's. The "notes on Hopi ceremonies" at the beginning is clearly Voth's handwriting.
The end of the volume contains copies of a few letters written by J. B. Frey.
It's not clear whether the dictionary entries are in Voth's or Frey's handwriting.