1976 50C Clad MS67 Certification #21637957, PCGS #6726
The U.S. Mint struck over 200 million coins for this issue making it very common. However, due to this one year Type design many collectors pulled these coins from circulation. Some saved them as conversation pieces or many times setting them aside believing that they have some significant value.
However, most examples in circulated grade are really common and only worth face value. Even some coins in Uncirculated grades up to about MS63 can still be pulled from circulation. Examples in MS64 and MS65 require some searching and considered scarce in these grades in circulation. In MS66 condition they become scarce overall with less than a few hundred examples known. In MS67 grade they are almost unheard of with less than a couple dozen known and none existing in better condition.