Slick left a vast set of correspondence spanning from 1938 to 1962.
The papers will be available to scholars and researchers interested in the origins of the biomedical and scientific enterprise in San Antonio and South Texas, the oil and gas industry, the history of the research institutions that Slick established, and his other interests.
This Cryptomundo article contains additional information on the cryptozoological interests of millionaire Tom Slick. He was an interesting guy. I imagine the papers contain some intriguing information for researchers.