OS is too short for the engine to deal with (I'll spare the tech details) but you can search for OS 40 by clicking advanced search so it sees it as a phrase. here is the search link below to this phrase search for "os 40". you can also use the rcu google search at the top of the search page for tricky ones like this.

http://www.rcuniverse.com/forum/sear...mitbutton=+OK+