Sugar Bowl - Swan Decal - RS Prussia?

Hello Everyone - I picked up this sugar bowl at auction not too long ago thinking it might be RS Prussia. After looking through the Marple books, though, I can't find this mold so I'm a bit lost. It stands a little over 5" tall and 6 1/2" from handle to handle. Somehow it got past me without a bottom shot but there's no mark. Thanks for whatever guidance you can provide. Don