Antique pewter Arts & Crafts brooch "Ruskin style" with green glass (?) cabochon

I inherited this pleasing little brooch from my mother, but believe it was her own mother's originally (b. 1891), so it is likely to be quite old. Similar ones online are dated anywhere from "Victorian era" to the 1920s, and are usually referred to as "Arts and Crafts" (1880-1920) or "Ruskin-style". I'm not sure what the latter precisely means where pewter brooches are concerned, but John Ruskin himself lived from 1819 to 1900.
Anyway, from what I've read, it seems this type of C-catch is very possibly Edwardian, as the pin doesn't extend beyond the diameter of the brooch. Of course, I'm not certain of that.
If anyone knows more about this type of jewellery, or has any ideas about either the date or the pale green cats-eye stone (which I suspect is simply glass), I'm all ears!
P.S. I was reminded of this brooch the other day when I saw kwqd's charming Battersea Shield pewter brooch here on Show and Tell (this has a vaguely similar vibe). As kwqd said, there is no category for pewter jewellery. Yet!