This is a computer generated add-on cachet created by Don Ashley from Bristol VA.  I purchased it from Don after placing the winning bid for it on eBay.  As you can see, the cachet features a colorful version of the traditional medical caduceus and the text "Crusade Against Cancer".  I believe that the cachet was added recently, probably sometime in 1999.  Some collectors look unfavorably toward add-on cachets, but if the cachet is attractive, I have nothing against them.  However, I do wish to encourage those creating add-on cachets to label them as such.  Years later, it may be difficult to determine if a specific cachet was an add-on or an original created at the time the stamp was issued.