Sportflics produced baseball cards from the mid-1980s into the mid-1990s. The cards utilized a technique called "lenticular printing" to make it appear that the image on the card was moving. They don't scan well but surely you've seen them. Or if not the baseball cards, you've seen other things made this way. The technique is still popular. How do they do that anyway?The 1994 Sportflics cards had two images. This one of Curt Schilling has two photos from different parts of his release so when you tip the card it looks like he's throwing the ball. The front of the card is covered with a ridged plastic. This is actually a lens, a lenticular lens. Each groove in the plastic is a lens. When you hold the card one way you see through one side of the lens, when you move the card you see through the other side. The picture may be either printed on the paper behind the plastic or directly on the back of the plastic. In the case of this card, the picture is printed on the back of the plastic. Here's what the back of the plastic looks like when you peel it off the card.
You still get the moving effect from the back, from light shining through the plastic, but it doesn't look as good. The other important part is the preparation of the picture. The two photos are sliced into thin strips and the pieces are interlaced. When you look through the front, the lens allows you to see the strips from one photo and then the other as you move it. Here's a close up of a portion of the back. You may want to click on the image to get a closer look.
You can pretty clearly see that the photos are interlaced. Look especially where the red cap of the one image overlaps the face of the other.