If you visit the posted coordinates, you will find some "Unknowns". However, you will need to also have (at least) the same number of mobile devices (with data connections and web browser) as the number of "Unknowns" you see. I guess one person could carry and juggle this many devices, but it works best (and is intended) to gather along with other cachers ... bring a crowd ...
Access the following website from each device while at (or very near) the posted coordinates: http://chilehead.us/mob/
A single, specific, known number will need to be entered on each device. This number can be calculated as follows:
1) Find the plaque which contains the phrase "ALL MEN ARE CREATED EQUAL".
2) There are four digits (any of the numbers from 0 to 9) on this plaque. Write them down, in ascending order.
3) Apply the following to the digits: +1, +3, +1, -1
If you have trouble reading the above, that's:
plus one (coma) plus three (coma) plus one (coma) minus one
4) And finally, re-order the digits in ascending order.
The resulting number will need to be entered when prompted "Which mob are you attending?".
Again ... remember ... each and every device will need to access the above site. Or, at least, as many devices as there are "Unknowns". And yes, I am keeping that particular number unknown and would appreciate if you do likewise.
However, please do let me know if there are any technical glitches or other things which preclude or prevent finding this cache. Thanks! And enjoy ...