I’d try to talk you out of the TM808 especially if you have mineralized ground. It’s basically a clc with a large coil. It was designed as an industrial detector for finding septic tanks, etc. Worst part is you think it is working but when I dug a three foot deep hole and put a post hole digger with a large head and it would not detect it, no matter where I set the controls. I had just sent it in to the factory for tuning and they said it was as good as new. I didn’t even put any dirt back in the hole. Not very happy. Pulse, pulse, pulse. An 18 inch coil can detect 100 copper pennys at a measured three feet deep with power and phone lines nearby.
I have a Minelab Equinox 600 I'm about to list, $500. + $15. shipping to the lower 48. Thanks