Hi Larry. In keeping with what SkiWhiz has said, let me add a little.
The Compadre, for the price(online @ $151.20), can't be beat for
a new machine. The Compadre has a factory "preset" GB which
enables it to work in most soils except highly mineralized areas
(iron oxides). It has a very fast "retune" speed so one can pinpoint
easily with back & forth short sweeps over a target while keeping
your eyes on the coil center & the target position in the ground.
This is quite easy with a little practice.
The Silver also performs as well as the Compadre but with the
addition of a Sensitivity control. What this control really does is
enable one to adjust the "Gain", or amplification of a signal from
the receiver coil to your headphones or speaker, which improves
the detection of targets, especially those "deeper beepers". It does
NOT mean that the transmitter EM field is being driven deeper into
the ground though, as again, it's only a signal amplifier. All Sensitivity
controls on detectors work this way. Also with the Silver, one can
interchange coils, whereas the Compadre has a hard wired 5.75 coil
only. Of course, the 5.75 coil is very efficient, being a smaller version
of the previous 7" coil, but just as effective, especially for areas of high
trash content.
So as you can see, both instruments offer excellent performance in the
field, given their design parameters, which are quite remarkable overall.
Good Luck in all your searches, whatever your decisions!
..W