Quick 45 min hunt this afternoon to get me out of the house. Pretty happy with the result. The brooch has "silver england" stamped in bottom, but no hallmark, so thinking junk.
I found an earring in the same style as that brooch - it just had 'SIL' stamped on it in very small letters. Think it's from the '30's or '40's - very old anyway.
Give it a gentle rub with soda-bi-carb, if it's silver it will clean up nicely if not you'll see where the base metal oxidisation is coming though any plating.