I found it in England for sale for 50 pounds..really almost new - I kept a 4 "Tesoro concentric coil / 5-pin / for my Mojave .. so I didn't hesitate and bought it ..

.This had a 4 "concentric coil ... there is no demon .. in the separation it works ok .., but again not somehow better than 5.75" concentric ....
4 "coil - I won't cut it on too much mineralized terrain - because even the" high ground "setting on Mojave doesn't work well with this coil, so overall I think coils 5.75" and 7 "... are the best .. and most universal coils for Mojave ... - I can work even in a very mineralized soil ... where the range on the dime is 4 "good signal and at a depth of 4.8" / in 12cm / in 6 bar mineralized terrain the signal is really borderline ..

I think a 4 "concentric will work well on ordinary US coins to a depth of 5-6" ... max .. and can be a good collector not too deep coins ...