I checked the fix. It had crystals in it but I mixed some up and sacrificed a roll of Ultrafine Extreme to test it. Sure enough, the silver halide cleared, so it was on to the real thing.
I put the film into the E-6 first developer (heated to 100F) for about 8 minutes, figuring that would produce some sort of image. Then into the fix. There are no images, but the film didn't clear, either. The strip is uniformly black. There are not even any edge markings, but that might be normal for this film. I assume that the film was fogged at some point.
I did confirm that Ilford Rapid Fixer is still good after being open for 2-1/2+ years.