This mystery cache is placed as a physical cache for completing the Great Falls Art Walk Adventure Lab series.
You get two of the number from each of the four individual series. After getting those 8 codes of the the 20 lab points you should be able to decipher the final.
To locate this cache replace the letter below with the number you will be earn at various stages of the adventure lab series
N 47° 3A.BCD' W 111° 1E.FGH'
Congrats to Li'l AL and SherpaRon from Kentucky on completing the 4 adventure labs and getting the FTF on this bonus.