Here is a permission form with liability waiver for those of you who need one. Feel free to modify it how you see fit.
Permission to Metal Detect on Private Property
I, _____________________________________ agree to allow (type your name and address), to use a metal detector to search for and recover buried coins, relics and other artifacts located on my property at ________________________________. In addition, I offer my service to you. If you or a family member has lost a valuable piece of jewelry or other significant metal object, I am happy to search and find it at no charge or cost to you. It is understood that recovery includes the digging of small holes, which will be repaired as nearly as possible to original condition. This permission will remain in effect until such time that it is revoked in writing.
________________________________ (Signature) ______________ (Date)
Liability Waiver Form
In consideration of permission to use a metal detector to search for and recover metal artifacts on the property located at ___________________________________ and owned by ____________________________, I, (type your name), agree to release from all liability for personal injury or property damage that I may suffer as the result of my searching said property. This release is binding and discharges said owner, his or her heirs, executors, administrators, from all actions, causes of action, claims and demands for, upon, or by reason of any damage, loss, injury which I may sustain while engaged in metal detecting on the owner's property.
______________________________(Signature)
_________________________________________(Address)
__________________(Date)