I am often amazed at the fantastic high-quality items we sometimes find are only marked "STERLING."
I can tell you the first impression I got was the resemblance to the 5 dollar "educational note" of 1896.
This was a highly illustrated 5 dollar bill that celebrated the bringing of electricity by a goddess (muse) to the people of the world.
The figure of the goddess looks very similar to the one on your cake slice, including the wardrobe malfunction which was initially scandalous to certain religious communities which petitioned to cover up the figural representation.
I can't really tell what this figure is holding in her hands but it could be a representation of the positive and negative poles between which stands the goddess, who represents electrical current. This could be a bit of a stretch of the imagination, or perhaps just a coincidental resemblance to the goddess of electricity.
The overall aesthetic is more consistent with circa 1895 as we see more art nouveau and Greek revival elements here.
Maybe someone with knowledge of the font of your "STERLING" hallmark will step forward and link it to a specific maker, hopefully so.