Its a very nice machine used very little,it doesnt say umax on it but it is the plastic case and uses a 9v battery. It has the White 9x8 coil. Is the air test on these machines not so great? Being adjustable ground balance I didnt worry too much about it but it did seem a little weak. I couldnt get a small pair of fingernail clippers to disc out either,I havent brought home any rusty nails lately to test. I took it out in the yard and ground balanced it and swept around a little,I got alot of great repeatable signals. I hope to take it to the 200 year old homesite I have been hunting tomorrow,I have been pulling silver and old nickel there with the gold bug se. I hope the tesoro whips the gold bug I am ready to go back to beep and dig.