I wonder about iffy signals all the time. The little suspender clip below discriminated below foil. Even then was an iffy signal. I'm trying to learn my new Vaquero so I dug it anyway. Glad I did.
Randy
I find with the iffy signals, it becomes a gut check. What is my gut telling me. Sometimes a screw cap or pull tab pop up, but when you think about it, why would this item be here in the middle of the soccer field? So dig, I did this last year and out popped a thin silver ring. I have found other items like this also.
Also, with new machines, iffy means dig! That is the best way to really get to know the detector.