mark
I hate screw caps, the aluminum ones especially as they fall in the conductivity range of a coin, the steel crimped rusty ones can be avoided with coil sweep technique. Like sweeping off center of the target near the edge of coil, that will usually break up the signal. Coins or other good metal will hang in there at the edge of the detection field on the outer edge of the coil... Or sweep your coil in fast short wiggles over the center of suspect steel bottle caps, that will break up the signal sometimes. Also by slowly raising your coil over the center of the target while still swinging your coil in short tight wiggles and listening how soon the target signal drops out is helpfull. Good targets will hang on to the signal longer as you slowly raise the coil higher while sweeping, and will indicate about how deep the target is located by how far above ths surface the coil is when the signal drops out. Of coarse, these techniques are to be used in the motion disc. mode.
If your detector has a true ground balanced, nonmotion, threshold based all-metal mode, you can use this mode to size up a target. Iron, large amd small (nails,steel bottle caps) will hang on to the signal longer and seem to have a wider signal. Good targets that are mid-depth and are not surrounded by nearby masking junk metal will pinpoint with a small, tight signal in the all-metal mode. Have fun & good luck.
