The “Challenge” is to find a cache in 100 different counties across the US. Any type of cache, in any state, can be used to help you meet the qualifications.
You will need to provide a form of evidence that you have qualified for this challenge: either a US County map (or a computed statistical output) generated by a geocaching statistic application and displayed on your profile page; or a list of counties with a GC number that you have found in each of the counties on your list. The list can be accomplished by creating a public shared bookmark list on this cache page, or by typing the list as part of your “found it” log entry. I think the easiest way to provide the required evidence is to use the stats generator found at mygeocachingprofile.com. Below is an example of the US County output that it provides.
The application is easy to use and uses your “my finds” pocket query to do all the number-crunching for you. You can easily copy-paste the HTML output into your profile page for all to see, or you can do a screen-capture of the output and add it to the photo gallery of this cache page by adding the image to your “found it” log.
The actual D/T rating of this hide is about a 1/1.5. The listed D/T rating is based on qualifying for the Challenge.
Good luck and have fun!
Congrats to EWB and cadrake for being the Co-FTFers!