Comparison and contrast is an important concept for children to understand. An easy way for them to visualize this and get their thoughts organized is through a Venn diagram.
Comparing and contrasting coins, will help your little ones remember them. By examinining and analyzing the similarities and differences, something will stick in their mind to help them differentiate.
I've made a coin Venn for each of the combinations of comparison. (i.e. penny with a nickel, penny with a dime and penny with a quarter etc.)
Students choose two coins, cut and glue them to their Venn diagram paper, so that they overlap a bit, and then write their results above the coins.