Detection method for Office MSP file or any MSP file.

HI,

I'm deploying an MSP file for Office 2013 after deploying Office. It has been created with the OCT tool. For the first deployment is fine but, which detection method should I use to see if the MSP has been applied already or not? I couldn't find a specific registry key. Generally, where can I find a registry for MSP files?

Thank you very much in advance,

Pablo