With the wind chill at -28, I decided to do a little bench testing. The indications will likely read differently in the ground, but this will give you some idea of where some gold coins might read. Sensitivity was at 5 with no discrimination.
$1.00 1851 = +9 with a low/mid tone.
$0.05 1995 = +10 with a low/mid tone.
$2.50 1855 = +13 with a low/mid tone.
$5.00 1906 = +18 with a mid/high tone.
$10.00 1893 = +22 with a mid/high tone.
$0.01 1946 = +23 with a mid/high tone.
$0.10 1998 = +28 with a high tone.
$0.25 2004 = +33 with a high tone.
Hope this is helpful.
OldeTymer
$1.00 1851 = +9 with a low/mid tone.
$0.05 1995 = +10 with a low/mid tone.
$2.50 1855 = +13 with a low/mid tone.
$5.00 1906 = +18 with a mid/high tone.
$10.00 1893 = +22 with a mid/high tone.
$0.01 1946 = +23 with a mid/high tone.
$0.10 1998 = +28 with a high tone.
$0.25 2004 = +33 with a high tone.
Hope this is helpful.
OldeTymer