This coil has been tested and works great.
LG30 SEARCH COIL (12"X9'') BLACK
Description: Waterproof DD Search Coil
Size: 30cm x 23cm / 12" x 9"
Including coil mounting hardware.
Most of these items are Amazon/eBay returns.
Ie: They got it as a gift and didn't want it. Buyer remorse. Had a change of thought and decided to take up basket weaving. Who knows?
This means most of them have never even seen dirt.