Question: I am doing research on the social security application (federal document #SS-5), and how it has changed over the years. Where can I look for historical versions of this document?
Answer: That's a tricky one since it says on the current form "Form SS-5 (08-2009) ef (08-2009) Destroy Prior Editions." The various editions of the Social Security Handbook include much information about the SSA's workings -- including about applying for social security with form SS-5 -- but does not include copies of forms.
So the next step is the Social Security Administration itself. The SSA has a History section that would no doubt be able to help, including 3 guides to SSA records. Lastly, you can contact the SSA historian to request copies of historic forms.