Board Thread:General Discussion/@comment-1409915-20141203211702/@comment-4854965-20141203234525

The code is a string of coded letters running along the edge of Dipper's Certificate of Mystery in Dipper's and Mabel's Guide to Mystery and Nonstop Fun.

Actually, I was the one that decoded it and posted it on this site under the cryptograms page. If you have any questions on it, lemme know