This guitar confuses me. If it was one of the original Japanese Mustaine Signature guitars, it would say "Dave Mustaine" on the headstock, and would have the "King V Pro" truss rod cover. If it's not a signature model, why would it have a Kahler. It's definitely Japanese with that serial number, and definitely an older guitar. The control layout also looks correct.
The Grover Jackson line, as well as the Jackson Stars stuff, is hard to get a grip on if you start from the perspective of the lines and models we had in the west. They´ve used a lot of Kahlers, for example. But yeah, this isn´t a proper Mustaine, just something very similar they cooked up.
late to the party on this one but would marker come off that easily on the white "grover Jackson" logo without staining it a little?. I do see in the earlier pictures what appears to be the marker smudge where the grover logo would be. Not too bad of a price for MIJ Mustaine influenced Jackson.