"the maker's mark on the back: four stamps: an 'L' in gothic script, an anchor, a lion, and the initials "R.Bs"."

It's English, from early in the Arts & Crafts Period. The lion passant is the British Standard hallmark indicating .925 sterling silver. The anchor is a City hallmark, indicating that it was manufactured in Birmingham, England. The "L" is a date letter; my guess without seeing it is that it's actually a lower-case Gothic L in an oval, which would mean it was manufactured in 1885 (lower case Roman L in a square; 1910) . The "R.Bs" is the maker's mark.