19th Century Ring Marked "STANDARD SILVER", Antique Shop Find

I bought this ring in a second hand/antiques shop just outside Coatesville, Pennsylvania in 2008. I paid $8.00 for it. This is what I found on the web in reference to the STANDARD SILVER stamp inside the band. This ring is, apparently, .900 silver:

http://www.ebay.com/gds/JEWELRY-AUCTIONS-Hallmarked-Sterling-Silver-Guide-/10000000002835019/g.html

"The United States has never used hallmarks per se. Indications of fineness or karat have been required since 1906, but fineness marks were sometimes stamped on silver jewelry in the 19th century (“coin” or “standard” for 900 silver, “sterling” for 925)."