You should only ever use the Perforce QAC Eclipse that was distributed as part of the Perforce QAC you wish to use. This is because API changes may occur between releases and so it is important to keep the version of Perforce QAC and Perforce QAC Eclipse Plugin in step with each other to avoid compatibility issues.
To check the Perforce QAC version, launch QA GUI and from the main menu bar, select Help → About Perforce QAC to bring up the ‘About’ dialog which will show the Perforce QAC version.
To check the Perforce QAC Eclipse Plugin version after installation, launch Eclipse and from the main menu bar, select Help→ About Eclipse IDE and then click ‘Installation Details’ on the ‘About’ dialog shown. Then find ‘Perforce QAC Feature’ in the list of items on the ‘Installed Software’ tab and inspect the ‘Version’ column.