I was with Greg when he found it.........It is his first ever non-junk ring and he just calmly announced, "Hey, I found a ring." No excitement in his voice, it was like he finds them with regularity! Myself and the other hunting partner were very happy for him....we were more edited than him!
Sorry Greg, I haven't had any luck on the makers mark yet.
The makers mark may be from the London assay group.......look up "Londonsilvermakers.co.uk"