Sterling Brooch with Three Opals (?)

This brooch might have looked golden in its earlier life. There is just a hint of gold left. The brooch is marked "Sterling" and has a makers mark. I have never seen this mark before. It looks like a pair of scissors with three blades pointing downwards. Maybe it's better described as two letters: one R reversed, joined by the second R.

Any ideas would be greatly appreciated.

Thanks for looking:)