Thanks for explaining the details on why an amperage meter should be used in further analyzing this drain.
In researching, found a thread on the radio causing the drain:
http://www.peachparts.com/shopforum/tech-help/368174-battery-drain.html
Is this situation possible for an aftermarket installed years ago with no problems but
now causing a drain?
In other words, if the radio was installed a long time ago and the battery drain is a new problem, should the radio still be examined as a possible drain source?