All Jap. sig. models are made in J-Custom (prestige)
No two JEM's or UV's (or Prestige's or J-Custom's for that matter) will ever be EXACTLY the same.
All of the signature models and the Prestige and J-Custom lines are HAND-ASSEMBELED & HAND-FINISHED by the guys in the J-Custom Shop. *You might get two that are really, really close, but if you break out the calipers, you'll find very small differences. *
The main parts (body and neck) are done with CNC for their basic shape. *After that initial cutting, they're selected by the guys in the J-Custom Shop as to which body becomes which model....and stays in their hands until it's done.
Think of the J-Custom Shop as the Callaway for guitars: *sure, a Corvette is nice, but for a few (or many) extra $$$, you can have a really nice, really fast product. *:-)
There is no assembly line for the Signature models, or the Prestige/J-Custom guitars.