how i know the original GPX4500

Hi Alkawa, welcome to the forum.

I am guessing that you are asking how you can be sure that a metal detector you want to purchase/buy is a genuine Minelab GPX 4500?

My advice is to:
1. Go to the minelab website (link below) and other websites and look carefully at all the pictures and brochures and manuals.
2. Try to actually see the detector, hold it and check it before you purchase.
3. Buy a new GPX4500 from an authorised minelab dealer (see the minelab website for your nearest dealer)

Link to Minelab 4500 images (360 degree views) from minelab site: http://www.minelab.com/aus/products/gold-detectors/gpx-4500?view=360

If you are buying via the web/ebay be aware there are people selling fakes or simply trying to get your money and not even provide you with a detector.
If you do buy off the web i recommend you find someone/email someone who knows detectors so they can give you an appraisal of what is for sale and the seller. You should also find out which dealer it was purchased from and the serial number (get a picture of the serial number if possible). You could contact Minelab and check on the serial number.

For a new GPX 4500 you can expect to pay between $AUD 5800 to 6200 dollars. because they are in demand at the moment the second hand price is the same price as a new one.

Other members of this forum may have other advice.

Tributer

Hi Alkawa;
Spot on Tributer.You've just about summed it up all in one hit.Also,when buying off ebay,if possible,buy it off someone who is in close proximity of where you live,who has a contact phone number,and who is prepared to accept,Bank check or cash upon pick up.That way you'll actually see what your getting for your bucks and have an address as well.

Cheers kon61