David;
I think personally that is a most excellent description.
I would add one thing, though not so much a statement but a further question. As we know many of the makers of the better grades of doubles did in fact make guns to order as regards stock dimensions at no additional charge in the beginning, some later when faced with declining sales & lower profits were forced to add a small fee. Would this be considered a "Custom Gun". In my opinion this did not really put it in a custom class. Thus if a gun is re-stocked with virtually all else as near as possible to original except basic dimensions as to LOP & Drop I would still classify it as a re-stock, not Custom as all guns of that make & grade would not have had identical dimensions.
