Ive used my F70 three times for a short while, each time adjusting the machine with advice from here on the forum. In my yard I was foolin with it just to get used to its sounds, and I got a 1934 Silver quarter at 8". My house was built in 1947. Then I went to our very old zoo, well worked over, and in one area got three wheaties, 26' 30' 36' , all at 6" plus- Im gonna hit some other well worked areas as I trust this machine is going deeper than my F4. With all that gravel and such, Im bringing my shovel instead of a trowel!