Much early American Silver was not marked with a quality stamp. Some makers used psuedo hallmarks that resembled English hallmarks to give an illusion that the silver they used met a standard. The D & C were some of the psuedo hallmarks commonly used.
Baltimore did for a short time developed a quality standard and required testing and quality marks on items produced there.
I suspect your spoons are what are commonly known as "Coin Silver" and the quality of the silver alloy may vary greatly.
I was able to identify two of the marks on your spoons. Andrews NORFOLK is probably Jeremiah Andrews of Norfolk, Virginia. Born in England he advertized in New York as early as 1774 as a jeweler. He moved to several locations including Philadelphia and even traveling to Savanah, Georgia for a short time before settling in Norfolk in 1796. He ran a succesful business there until his death in 1817.
Palmer & Bachelder & Co were a Boston firm in the 1850's.