You'll have no need for tones or an ID screen. The coins are usually just below the surface and often can be retrieved with just your fingers. In fact at the hunts I participate in, no digging tools other than a 3/8" wide or smaller, screw driver blade are allowed. You won't need to identify one type of coin over another, just dig, put in your pouch and move on, QUICKLY. Nearly every target will be either a coin or a prize token with the exception of the stray nail, piece of wire etc. Prize tokens (usually painted coins) are planted as well. The only good targets that might hit a bit weakly will be coins on edge and as mentioned they probably won't be deep. By the end of the hunt you'll probably be pretty sore from all the bending, kneeling etc. Some of the younger, more limber participants often retrieve 150 to 200 or more coins in the 50 minutes to an hour that each session runs. That's a lot of bending.
The hunts are lots of fun and meeting and visiting with other treasure hunters is an added benefit. I didn't think I'd care for this type of detecting, but once I tried it, I've attended each of the two that are held every summer close enough to where i live for me to be able to participate. I'm looking forward to numbers 22 and 23 this coming summer.
Go for it and have fun,
BB