Most American sterling is marked Sterling, 925, or 925/1000. Sterling silver is a minimum of 925 parts pure silver to every 1000 parts.
Prior to the enactment of the Stamping Act of 1906, there were no national laws requiring silver objects to be marked in any manner, although quite a few states had already adopted their own laws. The Stamping Act of 1906 required all items being sold as sterling silver to be marked as sterling.
Prior to 1906, marking a piece Sterling or 925 was at the discretion of the maker. Most makers, however, were proud of the fact their objects were made of sterling, and boastfully marked their items as such.
A piece may be marked 935, 950, or with another higher grade. This is still considered sterling silver, but has a higher silver content than that required by the sterling standard of 925.
The term English Sterling was occasionally used on sterling objects during the coin silver era prior to 1868.
Also during the time when coin silver was the predominant silver grade in the U.S., the Maryland Legislature passed the Assay Act, requiring all silver in Baltimore to be assayed. In 1830 the law was changed to no longer require the assaying of silver, but then required makers to mark their silver with quality designations. Silversmiths outside of Baltimore also started adopting this practice. Sterling silver is 11 ounces 2 pennyweight silver per 12 ounces Troy, so sterling silver from this place and time is marked 11.2 or 11-2.