short for HCO Security Form 3, issued as HCO PL 22 May 1961, The Only Valid Security Check, which laid down the policy that a Security Check for any organizational reason must be done from a n HCO WW form and no other is valid. It also gave further tech on Security Checks and contains, itself, an extensive list of Sec Check questions. The last two pages of the original mimeo issue of this policy letter deal specifically with overts against Scientology organizations, Scientologists and Scientology principals; in the lecture LRH refers to these as "the last two pages of Sec 3." —AcademyLevel I Glossary - Approved November 1990