What is now called the Viginere cipher was in fact invented by Giovan Batista Belaso in 1553 and differs from the Gronsfeld cipher in using letters instead of digits in its key. This not only makes the key easier to remember, but also increases the number of possible permutaions per key position from 10 to 26.
Before you attempt this cache, try to work out the key.
You can check your answers for this puzzle on Geochecker.com.