I hope you enjoy this geo-art as much as I have enjoyed placing all of the caches! You will find yourself needing to answer 16 questions about the history of Kalamazoo County, and based on the results of the coordinates for those 16 caches, you'll have the information you need to seek this final bonus cache!
*** There are 3(!) tokens in this cache for the FTF, STF, and 3rdTF ... please help yourself to one of them, if you're one of these three finders! ***
The difficulty rating on this cache represents solving all 16 caches in the geo-art and doing the required math steps. The actual difficulty rating for this cache is somewhere around a 1.5
Now for the nitty-gritty math to locate this cache! Take the N coordinates from all 16 solved caches in the series, and add just the minutes portion together -- the "zzz" in N 42 xx yy.zzz
So for example, N 42 10.050, N 42 12.253, N 42 15.540 would yield 50 + 253 + 540 = 843
Same thing for the W coordinates, add the minutes portion (zzz) together for all 16 caches
Now, you'll have a four-digit number from adding the N minutes, and a four-digit number from adding the W minutes. A checksum of a 4-digit number abcd is defined as a + b + c + d. The N checksum is 21, the W checksum is 27, should you want to verify your math.
Take the N number, and subtract 5211, call that ABCD. Take the W number, and subtract 4931, call that EFGH.
The coordinates to find this final bonus cache are: N 42 1A.BCD W 085 3E.FGH