Three databases I recommend for Guess Jean images from 1981 are Vogue Archive , Harper's Bazaar Archive, and WWD Archive. All of databases can be accessed from off campus or on, you'll be asked for an FIT login which is the same username/password you use to get into MyFIT and your FIT email account.
You can also search all three at the same time using the "change databases" option near the top of any one the databases' home pages.
For best results, I recommend doing an Advanced Search. This way you can limit your results to content from 1981 and you can also search for Guess as Company/Brand (one of the options in the drop down menu next to the search box).. Content can be downloaded/printed/email.
If you are not a current FIT or SUNY student or employee, you must request an appointment in order to use the FIT Library. Please see Visit the Libraryand submit your request through the form on that page.