Mastercoin is both a new type of currency (MSC) and a platform. It is a new protocol layer running on top of bitcoin like HTTP runs on top of TCP/IP. Its purpose is to build upon the core Bitcoin protocol and add new features, with a focus on a straight-forward easy to understand implementation which allow for protocol and analysis and its rapid development. Many of the functionalities are theoretical at this point (and ripple has first-mover advantage), but Mastercoin's definitely worth watching.

The official Miningwatchdog MasterCoin ticker is “MSC” and trades under that name on all the exchanges where it has been listed. The designation “MASTERCOIN” is for CryptoCompare.com only.