Cliff,
The CZ3D, in enhanced mode, is designed for the older sites you will be hunting. As long as there isn't much modern trash ( ie, tabs, aluminum, etc.) enhanced mode would be the way to run it, since that mode will bring some of the older coins such as V Nickels, Indian heads, etc. into the high tone category, where as the older CZ's like the CZ5 and CZ6a, may hit those targets as mid tone. Now, if you will also dig all of the mid tone hits, the enhanced mode vs regular mode on a CZ won't give you much of an advantage. If you run enhanced mode on the 3D in more modern sites, a lot of the aluminum and some tabs will hit as high tone....not what you want.
One of the main things to be aware when running a CZ in a lot of iron, is to run with the discrimination setting at 0. This may sound odd, but you WANT to hear all the iron tones, so this way, when there is an iron target that will bleed over and hit low tone, then high tone, you will hear the low tone. If you run a CZ with the discrimination setting at 1 or higher, the low tone of iron is now blanked out and you do not hear it. In the example where an iron target will hit low tone then high tone, with discrimination at 1 or higher, you will ONLY hear the high tone, and think it is a good target. For the first year or so using my CZ6a, way back in the early 90's ( still have that unit and it is still my go to machine !), I hunted a lot with the discrimination at 1, and dug tons of iron nails and rusty iron objects. When I started running in 0, and listening to all the targets, and only digging up REPEATABLE mid tone and high tone targets, and stayed away from a lot of low tone/high tone hits, as well as all low tones, I now dig WAY LESS iron. Sure, every once in awhile I will dig up a deep iron target, but target ID on most all detectors becomes less accurate the deeper the target.
For a deep, SIMPLE unit to set up and use, as well as adjust, on both land and salt water beaches, the CZ line is still at the top in my book. I strictly hunt by the tones, and never use a the meter, so I have mounted my CZ on a straight shaft, under the arm cuff, and it is one of the best balanced units I have.
JC