For pairwise combination, first choose 1 yuan coin, and there are three ways to find another one to match it. 1 yuan 5 jiao, 1 yuan 6 jiao, 1 yuan 5 jiao.

Let's take 50 cents. Only 50 cents and 1 cents, 50 cents and 5 points can match.

Finally, choose a coin with 1 cent, and only 1 cent and 5 cents match it.

So there are six kinds.