It is probably an indication that your ground is moderately mineralized. Some detectors often read low on deeper coins. Would you prefer a detector that IDs deep dimes in moderate mineralization as quarter-half bounce, or would you prefer the dime to read foil to pulltab? That is, which would you be more likely to dig?
Some detectors will read very deep coins as iron, but if you go by iron ID or iron is rejected, you'll miss it. Some detectors read so high on anything deep, that anything good or bad that is too deep for a real ID will read as dollar. Some detectors when something is too deep to ID will produce just about every ID. Some detectors have reduced visual ID sensitivity so nothing appears on a deep object, but it still beeps. Depending on depth & soil type, the accurate ID at depth may be impossible, or something that would greatly increase cost of detector.
You could try planting some coins at different depths, & make notes on how they ID. Like, at what depth does a dime read quarter or half, & does a really deep dime ID as dollar? Try same with a quarter. Even though the meter may be wrong at depth, it can still give you meaningful clues. If it always reads high, rather than low, or off in both directions, that is a good start in helping you figure out what you should dig & what it might be. Best wishes, George (MN)
