How to determine which Spectrum patches are applied

Environment: Windows

Version: 6.4, 7, 8, 9
In the directory where the Spectrum server is installed such as <SpectrumServerLocation>\Spectrum, you will find files with an extension of .rls. This is how you can determine which patches are applied to your installation.

For example, cdq9000S01.rls is the 9.0.0 S01 patch. 
UPDATED:  April 4, 2017