This is a Windows system installed file with Windows File Protection (WFP) enabled.
There are 26 versions of stobject.dll in the wild, the latest version being 5.2.3790.3959 (srv03_sp2_rtm.070216-1710). The average file size is about 134.37 KB.
(Note, the behaviors below are for all versions of stobject.dll, select a unique version for details.)
United States installs about 45.36% of Systray shell service object.