This caller is Sentry Credit, from Everett Washington.

No message left.  Typically I get another call like this, 10 minutes later, no messge from another number in a different area code.  I suspect this is a telemarker.  

Calls often and never leaves a message.

Called my mother and wouldn't tell her what matter it (the call) involved.

Leaves a message with no information on what the call is about.  Just tells you it is 'important' you call back.