I'd still go with what it says on the bottom, SEA. I don't think the piece on eBay is Flygsfors as it differs in many ways, thickness of the glass, colours, and shape.
I'd think it much more likely that the one on eBay is also Sea, whose pieces are occasionally unsigned. They did create pieces with the white line trimming the main colour. I've attached a picture of one of mine which is marked Sea.