Just met with a representative from High West. For the record, here's a breakdown of the sources of their products

Double Rye = 2yr HW rye and 16yr LDI rye
Rendezvous = 6yr (either HW or LDI, can't remember) and 16yr LDI
16yr = LDI
21yr = Barton rye aged in used cask

The 21yr is about to have its last bottling. 16yr is gone forever, get it while you can.