I sold my MKll so I could get the AT Pro a couple months after it came out. So, it's been a while since I used the Sea Hunter. As I recall, anything long and skinny like a nail or bobby pin will double blip when you swing the search coil over it lengthwise. I believe this holds true for any PI machine. Also, a nice gold cross will give the same signal.
Man, I'm trying to remember, but I think when I was using the MKll w/10"x14" Mono search coil, rings would double blip, too. Like, they would beep under each edge pass off the search coil.
Sorry, man, it's been a while. With any PI machine on the beach, you should really dig everything. I got tired of digging so darn deep with that Sea Hunter. It just goes ridiculously deep. That wore me out. That and digging every little signal. I did get some gold with it, too, though. You need the patience of a Saint to use a pulse induction machine. Just beep, dig, beep dig-repeat.
Make sure that you have a really good (really good) long handled sand scoop. You will NEED it!
Oh yeah, and Clive James Clynick has an incredibly good book entitled "Pulse Power" that I highy recommend you read if you use a PI on the beach.
Best of luck to ya!
Happy Hunting!