This calligraphy is Ryuten-sama. All priests and monks usually should have this hanging scroll. This is a very traditional and important thing for zen priests and monks. This is as a spirit that protects the practice and of the monk and his own dharma. We always hang it on the wall and recite a sutra for it in our own room after the morning service praying for good practice. 

The right line is written Ryu ten go hou zen jin as a spirit protects dharma.
龍天護法善神
The left line is written Haku san myou ri gon gen as a spirit protects the monk.
白山妙理権現

The signature of center line is written Sou tan kei syo by Rev. Soutan Tategami.
總担敬書
Sou tan is his name. 
kei sho is means written reverently. 
The lower part of seal ryou sen.
良泉
Perhaps his dharma name is Sou tan ryou sen or Ryou sen sou tan.
Ryuten-sama is usually written by a teacher, not necessarily a dharma teacher. 

This writer of Ryuten-sama is not Shunryu Suzuki Roshi.

Rev. Tatsugami probably wrote this for someone at Tassajara.

But this is a wonderful Ryuten-sama and should be treasured.

Gassho,

Shungo (Suzuki - Shunryu's grandson)

A couple characters are hard to read, but of those that are clear, I'd say something like: "May the Great Dharma Protector of the Dragon Heaven reveal the wonderful teaching of the Himalayas (White Mountains)." signed by so-and-so.  Bill (Porter - a close friend of Silas)