Well, any of the three could do well in that scenario.
The CZ-20 has 3 tones, 2 of which are of any value to you in that situation. Low, Medium, and High. Low is Iron, Medium is trash, gold, buttons, some bullets, and High is coins as well as many large targets, some bullets, some buttons, etc.
The Excalibur has many more tones...17, actually...to match the 17 frequencies. The CZ-20 has 2 frequencies. Like the CZ, it has no meter. But the tones can be much more valuable when you get to know them. So in that respect, I would favor the Excal over the CZ-20.
The Sovereign is not a beach machine at all. It's more of a land machine that happens to be a kick-butt beach machine as well. In fact, it's just an Excal that isn't waterproof. But it also has provision for a meter. And if you had that meter, then it becomes the better land machine than either of the other two. So with a meter, I would choose the Sovereign. In fact, I would choose it without a meter because it has a little better weight and balance than the Excal.
In closing, you could hunt with any of the 3 and do well. With the CZ, for a site like you described, you would dig all the Medium and High tones. If there were coins or bullets there, you would get them. With the Excal, same thing. With the Sovereign with the meter you have a bit more accuracy...assuming you were using a DTI meter or a modified Minelab meter with the 180 scale, a silver coin would be a 180, a penny a 176, a 3-ringer a 174, a musketball a 170, a nickel a 144...you see? VERY much better. If you had the meter. And if it was a stock meter than it would be 0 to 550 scale but there would be numbers that would correspond to all those things as well.
I recommend that if you have the 3 machines you mentioned, get them all, lay out some of the targets you expect to find, and practice swinging over them and pinpointing them with the 3 machines. Hunt with the one you are most comfortable with. It's that simple.
