Try listening for the “softness” or “ roundness” of the signal. Most coins & especially silver seems to have that “different” sound/tone to the signal. When you haven’t heard “it” in awhile, it kinda leaves your ears....but you will know it next time you hear it!
Also, keep in mind that coins/silver close to iron may have a lower number....and/or a jumpy number. Example...my nox loves modern nails. Typically get a 18-27ish jumpy signal a lot of times with the “softness, roundness” tone ( I assume it’s the round head on modern nails) ...but I typically dig them because I’ve dug silvers with the same jumpy numbers when close to iron or square nails. You can also use the pinpoint function to get an idea of how long the target is.....but I typically still dig these types of signals just to be safe.
I’m not a dig all guy, but remember the more you dig, the more signals you could possibly open up.
Also, you may only get a 1 way signal on coins close to iron depending on your coil positions....you can test this by laying a coin in between to rusty nails & seeing where the coil picks up all 3 other than just the nails.
Good Luck