It is important to know who your local finds liaison officer is. Any finds you are not sure of, or which may be deemed as treasure must be reported to them. Here are the details...
Finds Liaison Officer - Cheshire, Greater Manchester & Merseyside
Dock Traffic Office Albert Dock Liverpool Merseyside L3 4AX
Work T: + 44 (0) 151 4784259
What is the definition of Treasure?
Coins - All coins from the same find (two or more) provided they are at least 300 years old when found. If they contain less than 10% gold or silver there must be at least 10 of them.
Objects - All prehistoric base-metal objects from the same find (two or more).
All finds (one or more) at least 300 years old and containing 10% or more gold or silver.
Associated finds - Any object, whatever it is made of, found in the same place as (or had previously been together with, another object that is treasure.
Also, here is a good link...http://metaldetectingtours.com/htm/treasure_act.htm