Picked up a High Frequency coil for my Deus a couple of weeks ago to see if I could pull any more goodies from my old sites.
Last week I managed some buttons. Those high frequencies hit those lower conductors like those small tombacs pretty hard.
Yesterday I managed to sniff out a farthing from an old site. I think it was on edge and that 54 kHz is sensitive to small targets. I still have a hard time leaving iron in the ground even when I am 99% sure it is chunky iron.
Crusty farthing, but it gave up a date (1749).
Jeff