When metal detecting there are certain signs to look for.
Apparently one of the signs is seashells in a farmers field indicating a possible settlement site.
Bloke I used to work with a few years ago found a Roman belt clasp. Got over £14,000 for it at auction so bought himself a new Volvo car.
Unfortunately for the landowner Nobby, (the bloke I knew), had asked before searching if he wanted to go halves on any finds. The farmer said he wouldn't find anything so he, Nobby, got him to sign a disclaimer, (which he always does when searching on private land after getting permission), "just in case". He's had quite a few quid out of it over the years and gave me a handful of bullet casings once including some .303's and some 0.5's which he thought may have come from a Lancaster. Most of his searching is done in Norfolk.