The best wat to protect yourself and not buy a lemon is to research the guitar you are looking to buy. eg If you are going to buy a Gibson go to Gibson web site and down load the Gibson blue book this will tell you serial numbers for year of manufacture also various design changes and specs of all Gibson guitars.

Like wise for Fender and all other makes it is not in there intrest for you to buy a poor copied version of there guitars and in the past I have contacted companys and have always found them helpful.

Dont bid straight away put a watch it on guitar then research you might payless with more information.