Antique? Edwardian? Flat Straw Hat Sailor Pancake

I'm stumped by this one. It reminds me of the sailor hats worn by Victorian & Edwardian children, but I can't find any examples close enough to pin it down. No tags or labels. It's definitely very old. Navy blue. The top of the hat feels like straw and the underside feels like grosgrain ribbon. There is an old elastic at the back and a ribbon bow above it. The hat measures approximately 20.5" around the band (including gap with elastic) and the crown is about 11.75" in diameter. The front brim is approximately 4.5" at the widest point. The brim is about 1.5" in the back at the bow. It's a bit dirty and needs to be cleaned. I don't know how to clean these materials and left it as-is. The elastic is completely shot and the ribbon ends are frayed.