Fortunately, a good polishing will restore it. Most sterling made here after 1907 will be marked as to its quality and maker. The markings on coin silver are inconsistent, with some pieces bearing maker's and retailer's marks, while others lack any identification. To determine the difference between unmarked American coin silver and sterling without professional testing, examine existing marks that indicate the maker, whose country of origin or workshop should be recorded in reference books. The date on the monogram gives a good indication as to when a piece was made, if the monogram was engraved when the piece was made.
Many pieces bear several monograms, evidence of inheritance.
There are other decorations as well, patterns that reflect period styles. The challenge is in locating these pieces, as they have been spread throughout the country in the last hundred years.