Aluminum,pull tabs,pullrings and deep iron are a nemesis to any machine. Simplex is a sweet machine.
Make a test plot of good targets and junk at your home.
4-6" is deep enough to learn. At least a foot apart. Don't want signals inter mixing.
The longer items are in the ground in your test garden. The better the response from your machine.
The Simplex is not a beep and dig machine.
By listening to the sounds you'll get better.
The VDI numbers are more of a guide as to what the machine is thinking.
95 and up can be iron wrap around.
Look it up.
Disappearing targets can be iron Halo.
Or a very nice diamond earring.
As iron decomposes in the ground.
It creates a crystal bubble around the iron.
Most often a dissolved nail.
Makes a beautiful sounding target.
Most visible in sand. You'll see the black to orangy red as it grows away from the center of the iron.
When you dig you break this crystal matrix.
And the signal all but vanishes.
A simple long 1/4" screw driver pushed in next to the target and wiggled around a bit will usually break the bubble. A second swing then will usually reveal a good or vanished target.
Sometimes just a good heel stomp over the target will do for iron halo break-up.
With practice
Sounds=scratchy, trailing off ,blips peeps at end of swing, lifting coil to judge size and depth,width of signal.
Yes you have much to learn young paddyone.
Sorry I don't live nearby,Ohio. Oldest son lives in Peoria. Why this post caught my eye.
Practice practice practice.
Dig everything.
Noticing sounds and VDI's.
Watch Simplex users.
Curb Strip Chaos on YoTub is fantastic with the Simplex.
Good Luck
And Enjoy your new addiction !!!