Glazed Ceramic Stoneware Bowl - Maker's Mark ID help

So this is my first post, and how I found this online community...

I found this little gem at my Salvation Army thrift shop. It's a really excellent ceramic bowl. The outside has dimple texture and the high-fire glaze features several bands of color. The light, neutral colored foot looks like stoneware.

There's a geometric maker's mark design stamped into it. The mark looks like back-to-back R's with two dots in a circle or oval shape. Unless I'm looking at it wrong? And it's a W on top of a diamond. My gut tells me it's the first one.

8 inches across. 4 inches tall. Base is 3.5 inches. 1 pound 11 ounces.

I have searched hundreds of maker marks in hopes of discovering the studio or artist that created this pottery. No luck at all so far in my search.

Thanks for looking!

I was hoping Rookwood when I picked this up. It remains a mystery.