To find this last mystery cache, you will need to find the other caches in the series. The cache GC6BXKM : GCLT-1 has a "passport" for your collected stamps, that will in the end help you decipher this mystery cache location.
There is a little prize for your completed passport if you want - definitely for the kids. Please no close up photos of your completed passport so as not to give away anything.
The other caches in the series are: GCLT-1, GCLT-2, GCLT-3, GCLT-4, GCLT-5, & GCLT-6.
B.Y.O.P.
Enjoy your hike!