hay i have just aquired a gibson les paul standard in tobacco sunburst it has 3 yes 3 pickups! i have a feeling one is not orignal but not sure its a 4 piece body and 3 piece neck the seriel number is 512389 havent been successfull in finding out age(think its from 70s) if anyone knows more than me please email me or leave a reply...cheers

you have probably tried this already, but I just googled for that when I wanted to date my guitar. I expect there is a site somewhere that you can get that info off.

This is probably why they can't help you:

"Gibsons 1960-1975 serial numbers overlap depending on the various models ..it is best to contact an expert or Gibson with the model, color and serial # for accurate dating .. a semi-coherent serial# system returns in 1975 but still has a lot of overlapping depending on the year and the model....
Gibson Serial Numbers 1975-1977... (1975 still has many overlaps)"

Apparently you weren't talking to an expert. You need to be more forceful with them and pull rank or smooth talk them depending on whether it's a guy or a girl on the phone...