This is the process for determining if a custom rule is being used from the Sherlock output without the need to restore a database.
If you go into the Sherlock area:
There should be a file named:
If you examine this xml file and if you see a rule with an ID > 2000000 then it is a custom rule as per the documentation:
CAST AIP 7.3.x Documentation > Cookbooks > Platform Administration > Platform administration information > Assessment Model
Custom Customer metric IDs should be over 2000000