I've been rewatching Sliders again, and partway through the second season (episode titled "Post-Traumatic Slide Syndrome", there are two versions of Arturo fighting it out at the end - the original, and the one from the world they are on. Only one makes it through to slide to the next world, and it's not very clear which is which. Subsequent episodes seem to treat it like this never happened.
Has it ever been answered which Arturo made it through and which one stayed behind, either in the show, or other media somewhere? The wikipedia entry for the Arturo character seems to indicate this question was never resolved.