There are plenty of puzzle caches out there, but there are especially a good number of GR puzzle caches. Sometimes it's not made clear that the final cache is nothing more than a GR, which might make the experience slightly less worth it, and other times it's stated up front that for all the effort you pour into a puzzle, a simple GR cache awaits you.
For this puzzle, you'll know up front that once you've solved the puzzle, you're looking for a simple GR cache. To solve the puzzle, simply put the two words GR is an acronym for into Certitude, and then head off to find your GR cache if you choose to do so. Hope you enjoy.
You can validate your puzzle solution with certitude.