That image you posted with the large piece of iron and a small dime is something that would affect every detector, with some detector and coil combinations suffering more than others. But even those that might get a hint of a good signal on that arrangement could still struggle if it was swept from a different angle, with different settings, or with a different coil.
It doesn't matter if it's a site that was impacted by bombing or similar activity, or any old site that has a lot of discarded debris, they are all metal-targets we have to deal with and all of them based upon their size, shape, orientation hand metal alloy makeup are going to be detectable. All will have an effect on an electromagnetic field, so it boils down to the size and shape of that electromagnetic field coupled with the circuitry design an ability to deal with how those types of metals, and sizes of metals, affect the electromagnetic field.
I have trim to my working detector outfit down to 10 detectors as of today. Some of them are a little better for coin hunting in more open areas with a reduced amount of trash targets, while others have more strengths and abilities to take on unwanted debris that is more closely associated to cause more negative performance target masking.
I am hoping this new Garrett Apex, hampered by only having one search coil at this point, might work reasonably well in what each of us might consider an 'average' type of environment and make useful general-purpose detector. Search coil size, shape and type plays an important role in performance. Circuitry design of the detector also is important. From my experiences, in average conditions two very heavily iron littered sites over the past 5 years and 7 months, has proven to me that all of the different Nokta and Makro detector models I have and continue to enjoy handle some of the tougher challenges as well or better then most of the competition.
Nails, bolts, washers and other ferrous - based objects are going to have a different effect on an electromagnetic field, or ability to be identified, compared with a lot of the non-ferrous metals associated with bombing activity or other explosive ordinance.
Monte
"Your EYES ... the only 100% accurate form of Discrimination!"
Stinkwater Wells Trading Post
Metal Detector Evaluations and Product Reviews monte@ahrps.org ... or ... monte@stinkwaterwells.com 503-481-8147Detector Outfit: A selection of my favorite makes and models, with the best coils mounted, for the tasks I'll take on.Pinpointers: Pulse-Dive & ProPointer AT .. Headphones: 'Hornet' & 'Wasp' .. MS-3 Z-Lynk .. ML-80 .. N/M Green edition*** All working well today to make memories for tomorrow. ***