Hello, I managed to "blow" the marks the marks up a little bit and interesting they look. But obviously not hallmarks as there is no silver guarantee mark. I think we are looking for a "JS" plate manufactuter. There is a "Cog/Star" mark, possibly a elongated "crown" mark and "conifer tree" type mark. Sorry I am not on my own WiFi at present and I cannot upload the bigger image. That collection of marks are as you might find in the middle to later 19th century.
I have sugestions, John Sanderson of Sheffield and a Joseph Smith referenced on "silvercollection.it". I am sure a enlarged photo of the marks would get further responses