Hi John,
Suifu (水府) is the name of a village in Hitachi province. The formatting of this mei is slightly unusual, with the two characters of Suifu being arranged horizontally (and read right-to-left) at the top, and one would ordinarily also expect them to be followed by "住", but I guess the smith took some artistic licence here.
The sugata does not suggest tantō to me – it rather looks like the fragment of a longer blade (wakizashi or katana) where someone crudely attempted to shape a new "kissaki".
Most of this is beyond my reading skills, but the characters in the leftmost column in the first and fourth images are a name:
山田耕三郎 (Yamada Kōzaburō, probably this guy).
I believe it says: 嶽家劍法 (something like "Yue family sword fighting style"), where Yue refers to the Chinese Song dynasty general Yue Fei (嶽飛) who was known for his martial prowess.