You will get to where you recognize targets by sound. The E-Trac is set up for all the good targets to show up on the Fe 12 line, however the FE number can fluctuate according to depth and ground conditions or other targets above or below or next to your good target. For instance you may get a solid sort of warbled signal and the numbers may show up as 35-46. This could be a US quarter with a junk target above or below the good one.
12-36, 12-37,12-38 are usually junk zinc penny's. Your 1982 and older penny's will come in at 12-42 12-43 and dimes will also show up as 12-43,12-44. If your in an area that may produce Indian head cents you don't want to pass up 12-33 to 12-38 because that is where they come in at.
The more targets you get out and dig the more your relationship with the E-Trac will grow and you will see how well this machine separates the good targets among junk. Personally I listen to the sound, but I do find myself looking at the CO number which my brain usually relates the sound with the number and I associate it with what I will be digging. Of course with any detector it is not 100% fool proof.
I just purchased an Excalibur II 1000 and it came in yesterday, I have already tested coins and several items of jewelry to listen to the tones, then I hit the neighbors yard and dug some penny's and pull tabs 4 to 6 inches deep. I think I will love this machine on the beach while on vacation this year. The E-Trac is an awesome machine for the beach too, too bad it is not waterproof.
Good Luck
BCOOP