I'm guessing this hails from the 1970s, but the level of naivete suggests the paternal 1950s to me.
This document reminds me of early postcard-type applications for in-store credit cards. They similarly advised you to write down pertinent personal info in writing on a tiny scrap of paper and send it in the mail, where countless eyes would peruse everything needed to appropriate your legal self. A post about this is here.