There was a good bit of Dutch 'historical' silver (along with Hanau) that was retailed in the U.S. from the late 19th century, and there was also wide American production of mostly silverplate 'Dutch silver reproductions' (along with the ubiquitous 'Sheffield reproductions') in the 1910s-20s. Some time ago, found mention in a 1919 travel guide, of "fraudulent antique Dutch silver" supposedly manufactured in New Jersey - but suspect that if true, it would have more likely been marked with something akin to the marks found on the Dutch and German pieces. This mark strikes me as one that could have been used by a maker from any number of places, with the hammer being a tool universally used in the trade - do suspect, if American-made, it would have dated from the late 19th-early 20th century and most likely been marked as 'Sterling'. Does seem to be a mystery at this point...
~Cheryl
1919 excerpt:

Similar 'hammer' mark used by Sheffield cutlery manufacturer William Gregory & Sons:
