Back in the 70s and 80s, you might actually see someone wantonly waving a metal detector around in the vague hope of finding a roman coin or sword. These days this sight is not common at all, mainly because all the roman coins have now been found. George knows the plight of a metal detector all too well when he asks his question. To ask if anything at all had been detected, he may get the solemn story of only finding a rusted tent peg. He wants to know about the juicy stuff - a bullet casing, a WWII helmet, a discarded Grammy Award.
Notice that George uses the word 'detect'. If he had used the word 'found', would it have given the man licence to tell the story of his affair? In fact it may have given him licence to tell more of the story. Imagine if you will:
"Found much of any importance yet?"
"No but my wife has."
"What did she find?"
"A pair of knickers belonging to the next door neighbour in the glove compartment of my car. I've been having an affair with her you see."
I'm sure the irony of the man finding a horseshoe is not lost on him. You see a horseshoe is lucky and he certainly hasn't been lucky. Well, he was bound to get found out sooner or later, it was his next door neighbour for heaven's sake. Is the last scene the the thoughts of the man or the collective thoughts of George and Lynne trying to imagine the situation? If it is the thoughts of the man then he has done very well because the woman in the foreground, who must be the next door neighbour, is very attractive and certainly younger than him. If it is the thoughts of George and Lynne then they have very high opinions of the man to imagine that he would be having an affair with such an attractive woman. Then again, any man with a metal detector is bound to have women swarming round him.