The target switch is a 3 position momentary switch that returns to the center position after it's been pressed.

When hunting in disc mode, when the switch is pressed up to the zinc position, it will disc out targets that have the conductivity of a zinc penny & below. Meaning that the X5 will beep on targets that are a copper penny & higher in conductivity.

When pressed down to the nickel position: It discs out targets that have the conductivity of a nickel or below. Meaning that when it's pressed down, and the signal GOES AWAY - then it very well could be a nickel (or small gold ring... or yes - possibly parts of a shredded aluminum can)...
The biggest benefit of the target check (TC) switch - especially when coinshooting, is to let you know precisely what "range" your target is in... Those pesky pull-tabs will beep when the TC switch is in the nickel position, but will go away when it's in the zinc position.

Soooo... If your target goes away when in the zinc position, and still goes away when it's in the nickel position... Then "Dig it". It could be another small gold ring that has been overlooked by other detectors...

G'Luck!

Rex