Estate Brooch with Anchor Hallmark

This is an estate sale purchase and I really love the brilliant yellow gold color of this piece. I call it my Harvest Brooch since it resembles flowing strands of wheat (to me anyway)... LOL.

Anyway, I'm curious about the anchor hallmark on the back of this piece. I've done some research and the only thing I've come up with is information that leads me to think that it may be a British hallmark. The third photo is where you can see the mark when zooming in. I'll try to post an even clearer closeup.

Any help with this hallmark question is greatly appreciated! Thanks.