Things to look for in Auctions.

Pirate Gold or Doubloons -
A number of vendors sell these and they are usually gold coloured rather than gold.
There is no intention to sell these as originals - read the adverts carefully and you will see phrases
similar to or in the style of and similar things that mean they are reproductions.
Real Pirate coins should come with a guarantee of authenticity or a certificate.
 
Please be careful about fake Gold Panda coins - there is an article on ebay showing the difference between real ones and reproductions.
 
In all of the coin sections there will be vendors selling unsorted collections but it is unlikely (but not impossible) that you will purchase any gold coins in unsorted lots unless you are very lucky.
 

Read these before purchasing.

http://reviews.ebay.com/Unsearched-lots-of-coins-GRAB-BAG-SCAMS-on-EBay_W0QQugidZ10000000001225730?ssPageName=BUYGD:CAT:-1:SEARCH:3
 
http://reviews.ebay.com/FAKE-GOLD-SCAMS_W0QQugidZ10000000001003873?ssPageName=BUYGD:CAT:-1:SEARCH:4
 

http://reviews.ebay.com/Fake-Bullion-and-Gold-Chain-Scams_W0QQugidZ10000000001382296?ssPageName=BUYGD:CAT:-1:SEARCH:5

You should read the reviews before bidding.
 
ALWAYS check vendors feedback before purchasing.
 
Some Private auctions do not allow you to see feedback.