If you are a coin and jewelry hunter using a metal detector with a VDI screen here are a few reasons why target IDs should only be a potential estimate of the metal object detected.
Numbers, numbers, numbers, everyone seems to be obsessed with Ferrous and Conductive target numbers, but several different things can throw throw target numbers off on a metal detector screen.
Typical FE-CO number responses from commonly found coins or rings laying flat buried in sand or soil are usually going to be the same nine times out of ten.
Place that coin or ring on edge at the same depth and the FE-CO target numbers will probably read differently.
The angle you sweep over the target may also effect the read out, especially if you happen to detect another metal object close to the initial target, add saltwater washing over the area and watch those target numbers change even more.
I always advise people using a metal detector with a screen to just use target ID numbers as a second or third opinion, the first opinion when using a metal detector is always made by listening with your ears.
Hunt by ear and use your eyes to scan the ground you are metal detecting over, if you are searching for old treasure coins and artifacts always trust your ears over target ID numbers.
Searching for modern coins and jewelry, make sure you know the target ID numbers darn well before skipping over stuff because you are certain something has been identified correctly.
I have recovered plenty of impressive 10K gold rings that responded with stinking Lincoln numbers and chunky silver rings disguised by typical quarter target numbers.
One of best uses of target ID numbers is to identify nuisance objects in areas littered with what ever the nuisance object is in the area being searched.
A few years ago I had an excellent beach hunting opportunity in an area littered with old fashioned roofing nails, I knew what roofing nail FE-CO numbers came up on my Minelab CTX 3030 screen and I spent a couple of hours detecting and and removing the roofing nails.
I purposely went after and removed the nuisance target because I knew they had the potential to mask the old gold coins I was searching for, being able to identify but not dig the trash was not a good option.
This was a perfect example of knowing how to use one of the so called bells and whistles of the Minelab CTX 3030.
Another good use of target ID numbers is searching for high potential targets in heavily hunted areas, about the only time I will play the percentages by skipping targets with the Minelab CTX 3030 or Equinox.
There are times to rely on FE-CO target numbers on metal detector screens, just not all the time.