Use one of the following methods to find Oracle WebLogic Server version

1. From registry.xml in MW_HOME
Go to Middleware Home under which WebLogic is installed and look for file registry.xml
Open registry.xml and search for “component name=”WebLogic Server”” version=”″  (variable version next to this will tell you weblogic version)

2.From WebLogic Admin Server logfile at $DOMAIN_HOME/servers/AdminServer/admin/AdminServer.log and search for “WebLogic Server“. Output like below will tell you WebLogic Server version ( as per output below)

WebLogic Server  Fri Dec 17 20:47:33 PST 2010 1384255  Copyright (c) 1995, 2009, Oracle and/or its affiliates. All rights reserved.>

3. From class weblogic.version 
Go to directory which contains weblogic.jar ($WL_HOME/server/lib) and run below command

java -cp weblogic.jar weblogic.version

You should see output like
WebLogic Server  Fri Dec 17 20:47:33 PST 2010 1384255
Use ‘weblogic.version -verbose’ to get subsystem information