Got any ideas?????????????????

Dig those weak signals, 99% may be junk but there is always that chance. Second, do not rely on the visual display. Some of the older coins were different compositions than the newer ones and will not ID correctly, also deep coins or those on edge or near junk items may not ID correctly. You must remember as well, even one cent had buying power in 1901, people were more careful about losing coins, and would search harder if one was lost. Finally, practice, practice, practice, the better you get with your machine, the more you will find.

Your observations about good and bad signals are for the most part correct depending on the depth. For me if a target is 7" or more I can't rely on a good signal in all directions. I've had targets at 9" that weren't much more than a whisper in only one direction that turned out to be silver. Also a coin on edge or near trash will do the same at even less depths.

If the targets you are digging are fairly deep then it could be you need to work on technique. Slow down and make sure you're overlapping each swing by at least 1/2 the width of your coil. It could also be you're in an area with a lot of other MD'ers but even these places are bound to hold a few goodies missed by even the best hunters.

Section off, in your mind, a 10'x10' area and concentrate on it only. Remember that the detection area of your coil, unless you're using a wide-scan, is only about 2" at 6" so cover that 10' area good and in all directions.

I don't know about the GTA 350 but on the detectors I have owned older coins in most cases do show up different. An older dime or quarter will read higher because they are silver. On my Spectrum I could tell a clad dime or quarter from easily. The same is true on pennies. The new zinc pennies read much lower than the older copper ones BUT the really older pennies such as Indian heads read lower yet. My hunting buddy and I used to make a game out of guessing a targets before it is dug.

I'm not sure how long you've been MD'ing but be patient and in time you'll start hitting the old stuff.