I can't tell much from the picture, but I can tell enough to know that ain't no Putt'r. I did forget about the APX, though. Does that disc have a bead? I really can't tell.
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The Magnet has no bead and tooling on the bottom that says "Magnet." The APX looks a lot like a Magnet with a bead. I have some APX with no tooling and others that have tooling that says "APX" on them. I have no knowledge of a run of Z APX, but I know enough to know that doesn't mean they don't exist. The Z Magnet did exist. The Challenger didn't come out until '03.
All that adds up to a bunch of "I don't know." Did you check the tooling?