fotofila,
The spelling of the kanji is the same as "Ueno" but this one reads "Kozuke". "Kozuke no kuni" means literally "the country of Kozuke" and it is the name for the province during the Shogunate time, the present Gunma prefecture.
http://en.wikipedia.org/wiki/K%C5%8Dzuke_Province(the kanji "kuni" is written in the old format on the stamp, Wikipedia puts the modern one)
Sherri,
I think it's a company seal vignette of Watarase-kumi. I have found a pdf file of the Takasaki Keizai University mentioning about Watarase-kumi.
Here is the fragment of the passage talking about it, Watarase-kumi is a silk producing company founded in Meiji 10. It looks like they have been mainly exporting to the US according to this document.

here is the link for the pdf, it has an english summary at the beginning.
http://www1.tcue.ac.jp/home1/k-gakk...tomizawa.pdf