For the most part when hunting - I run my 2500 in 'all metal slow motion mode'
NOT in "true all metal" (as there is a big difference between the two). Non motion all metal mode should only be used in clean ground where you don't pick up any shallow junk signals, and or in highly mineralized ground. In slow motion all metal mode, I notch out the 1st 3 notches to avoid nails, and tiny iron objects (yet) it allows you to pick up on small/tiny gold rings, etc.? If I'm in an extremely trashy area where there are a lot of iron pieces, scrap alum. etc., I'll switch to coin/jewelry mode and run it at the preset setting as, it will mask out some of the junk yet still pick up gold, etc. I never use "Treasure Talk" as it is annoying to say the least and has no viable benefit other than driving you nuts! Keep imaging on, ground trak on, salt elimination off (unless hunting at a salt water beach). Keep the back ground light off unless it's really dark (to preserve batteries). I use "Bi Level Audio" to hear 2 different tones to help in target identification, and switch back and forth from all metal slow motion mode to coins/jewelry mode to help further identify target composition when in doubt as to if it's a good target or not!
You will learn your 2500 and what is best for you at your location/s and under what ever conditions, etc. The above is just my experience of what works the best for me in my area, and in helping to get the most out of the machine with out discriminating out too many of the good metals (mainly gold)!
Good luck, and HH, it's a killer coin/silver and decent jewelry machine with awesome depth in "True all metal mode" for relic hunting, etc. too!
P.S.
as for imaging ID,
A size targets are always dug as they are good possibilities for smaller rings, etc.
B size targets are always dug because they are mostly coins or the like and or med - larger rings, etc.
C size targets are always dug because they are Large coins, and or toy cars, relics, etc.
D and E size targets are "iffy" and you need to use your own discretion to the identification of the target as these tend to be large and very large targets. Listen to the sound of them, and depending on where you're hunting at, use your better judgment as to dig or not!
Lonewolfe