Nokta Makro Simplex metal detector and rusty bottle caps

This is a video showing the one main flaw with the Nokta Makro Simplex metal detector which is rusty crown bottle caps ring up high and solid in the ground. In the video I demonstrate how a rusty bottle cap rings up high and near the same as a copper 2 cent coin on the detector when buried in the dirt. Also I have figured a way of determining whether a target is a rusty and non rusty crown bottle cap or not when it's on the surface or just under the grass. As seen in the video I set the preset to all metals and swing over the cap and as seen it mosty rings high in the 60s and 70s but there's some extremely low numbers in between less than 5. Unfortunately when the cap is in the dirt it will stay high on detection no matter what.