This cover really doesn't have a cachet, but its return address was interesting enough for me to include it.  The Detroit Institute of Cancer Research apparently created these covers for their own use.  I've done a little research of my own and it appears that this Cancer Research center no longer exists, or at least not under the same name.  My copy contains two small stains that are not that much of a detraction.  If you can provide any other information about this cover or the Detroit Institute of Cancer Research, please drop me a line at smith@in.net.