Holy Win (or 'Excalibur', as the blade alone is known) is based on the Iocus Rood, I believe. The Rood Inverse, with its dagger centrepiece, has a distinctive look. The blade is broad near the hilt, and tapers quite a lot, down to a point. The central blade of the Holy Win, and the central strut of the Iocus Rood, are of a uniforn width along their length. (SPOILER)Also, just prior to the Guildenstern fight, the Holy Win can be seen as a decoration of the dome at the top of the Temple. When Guildenstern first begins to embrace the dark and transform, it seems he removes that decoration to use as a weapon. In the temple itself, there are several statues of robed women carrying smaller versions of the Iocus Rood, perhaps a foot and a half long. This suggests that the design might have originated from a multi-bladed sword in the first place, though this is pure speculation.