Move your cursor in and out of the images to alternate an overlay display of the MSScvm cloud mask.

The algorithm is certainly not perfect, but given the low radiometric and spectral richness of MSS data, it does pretty well. It has high accuracy for thick clouds and their shadows, but there is moderate omission error for thin, semi-transparent clouds and their shadows. Additionally, there is cloud commission error for extremely bright surfaces, as well as cloud shadow commission error for dark surfaces west of clouds. Take a look at the examples below to get a sense for its suitability for your application. Note that the display images have been quantized to 6-bit color for better web performance.