Because the card is worth a fortune, fakes are everywhere on eBay. Real copies have a specific holofoil pattern that shimmers like a rainbow. The card stock is thicker than normal cards. And the back’s Egg design should be crisp, not blurry.
If you ever find one in an attic, don’t touch it with bare fingers. Oils from your skin can damage it. Immediately put it in a protective sleeve, then a hard plastic case. Then call a certified auction house. You might be sitting on a retirement fund.