One of the easiest and quickest way to identify a fake guitar is to look at the ESP logo. This is characterized by being made flawlessly using glitter paints. A quick glance at these logos will let you know if the guitar you are looking at is a true ESP or a Chinese one...
Old "ESP Custom" logo have this dimensions:
- "ESP" about 39x16mm
- "Custom" about 23x6mm
the space between "ESP" and "Custom" can vary, I think because they were 2 different silkscreen frames and the print were made manually.