I THINK there are a few differences. If memory serves me rightly, the GK was the '03-'04 model but it may have been introduced earlier. This model has larger
neck inlay dots and if it's the same as my '03 1527 it uses a 3-piece neck with a
scarf joint. I have an '05 1520GBP, and it has the nicer small inlay dots and a 5-piece neck with a volute instead of a scarf joint. I'm just making an informed guess on the neck of the '03 by the way.
Electronically I think they're identical.
It's a sweet guitar and FAR FAR superior to my other synth guitar, my Fender Roland-Ready MIM Strat.
I hope this helps.