Prussian geography help?

I have a GEOGRAPHY question relating to my family line. The basic
information I have about my heritage came from my father who shared a
document from my great-great grandfather who was apparently in the
service of the king as a blacksmith, and was "released" from service in
1868 when he came to America. In the document it states that my
great-great grandfather "from the village of Sommin, the county seat of
Butow" is granted permission to leave the "All Prussen service" from the
Royal Government. It is signed by the "Minister of the Interior/All
Prussen Government".
     Aside from the document, my father also told me that my great-great
grandfather came from the Village of Sommin, in the Province of
Pomerania, of the Country of West Prussia... I've been told that these
geographical references do not match up. Could someone explain what
seems right/wrong with these references? As mentioned I am still
learning and appreciate any guidance. Thanks in advance!

Good morning,

http://www.library.wisc.edu/etext/ravenstein/home.html

This map is of the German Empire (1871 I believe).

The above is a download source available for the
Ravenstein Atlas, digitized, from the University of
Wisconsin-Madison library.

In order to view this Atlas online, you will need Adobe
Acrobat Reader (3.0 or better). If you do not have
Adobe, the information page has an address for a
free download.

This German Empire Atlas map is broken into eleven
different sections of the Empire. The information page
will give you sections and section numbers of any
particular area(s) that you should choose to view or
download. Ost und West Preu�en being 3A and 3B.

Also included on the information page is a city-village
locator provided your city-village spelling is identical
with the Atlas version.

On the sections that I have downloaded, I set my printer
on "best print" and use photo paper for the best results.

Also keep coffee handy because it takes a while to
download because of the detail of the mapped areas.

On another site, someone contacted the University and
was told that a CD was in the process of being made
for sale to the public because of the demand. I have
no dates or cost information or if the detail off the CD
will be better than what you will be able to download.

Let me know if you use this download and how it went.

Regards,
Robert Lipprandt
(South Florida)