When buying Pokemon cards from eBay you want to be able to identify various types of scams one of the biggest is with the orignal base set Pokemon cards. People will try to make you think that shadowless cards are some kind of error print or misprint of Pokemon cards when they are simply what the cards started as. Back when Wizards of the Coast was making cards the first edition cards all came without shadows. Then they made the change to do the non first edition unlimited set cards but decided later during the printing that they would change this by changing the print of the unlimited set and give them shadows they changed the print on the card as well.
These changes can be confusing to a collector because since the base set is one of the most printed and scammed sets. Especially since it is very valuable. If you find people claiming they have a first edition Pokemon card with a shadow then its a fake using one of the unlimited cards with a first edition stamp on it. Identifying trainer cards and energy is easier by checking the printing on the card it should be ©1995,96,97,98,99 Nintendo,Creatures, GAMEFREAK 1999 Wizards with the year 1999 printed twice on the card like the above.
The Machamp Pokemon card is the only card which comes in first edition shadowless and first edition with a shadow otherwise all of the other Pokemon cards that are first edition will always come shadowless. Shadowless Pokemon cards from the unlimited set are still pretty rare and most of the first edition cards are very rare just because these are out of print and with people trying to scam people using shadowed version of first edition cards if you can manage to pick up real cards from these you will eventually have quite a lot of money in the future.