The purpose of this cache is to bring you to an engraved plaque which commemorates the signing of the Portsmouth Contract, a document that established the settlement of present day Portsmouth. In addition, it was the first document in history that severed both religious and political ties from mother England. (source)
The posted coordinates will lead you to the plaque, in which you will need to get some information from. It is possible to view a picture of this plaque online, but it is strongly recommended you visit it in person to get the full effect it offers. Use the simple formula below to find the cache, which is nearby:
North 41° 37.ABC West 071° 14.DEF
On the top of the plaque you will see two dates: 16B8 - 193A.
C = The number of letters in the third word on the plaque under the two dates listed above.
D = The number of men named John who signed the document.
E = The number of letters in Randall's last name.
F = The number of letters in the first word of the paragraph underneath PORTSMOUTH COMPACT.
Once you have your numbers, you're looking for small tube and will need to bring a writing utensil. The cache is NOT in the stone wall, so please don't look there or even think about touching any rocks. Please rehide the cache as found, out of view and well hidden. Thanks, and hope you enjoy this little piece of history and the park!
If you need to, you can check your answers here: GeoChecker.com.