It's tough trying to teach students to count coins when they may not have much experience in handling money. Pictures on a page are notoriously imprecise. Plastic coins are better than nothing, I guess, but it still seems that students need to have handled real coins in order to recognize the plastic ones.
Here's one way to give students a good visual and tactile experience of coins. The card is matting, 8-ply. It's a thick matting and often can be obtained as scraps from framing or craft shops. The text was copied several lines to a sheet of paper, cut into strips, and then cut to fit the length of the cards. Then I use clear tape to attach the strip of text to the bottom half of the card. Unfortunately it can't be laminated -- I don't know of a glue that will stick well enough to laminating material.
The coins are glued to the card using 100% silicone caulking, just a large dot on the underside of each coin. You'd really have to work to pull those coins off. This gives students a chance to feel the coin as a 3-dimensional object.
The best solution, of course, is to have students using real coins. I'll post my method to do that in a few days, after we're back in school.