First off, it's a Mac Plus, not a 512K. Facts don't match with what the guy says.1) The front says Mac Plus, the back says 512K. This indicates that the back of the casing was changed.
2)The labeling on the plexiglass sides makes it appear to be a show model for the Hyperdrive upgrade.
My diagnosis:
It's a Mac Plus, with a modified back case. Not a prototype, but possibly a modified show model.
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