Andy S. coin program misses 2 stacked silver dollars?

[ArkieBassMan]

While air testing (before you say it...I know...not 100% reliable) my e-trac today, I saw something that surprised me. One silver dollar came in at an expected (from watching YouTube videos) sweet-sounding 1-40. When I waived 2 stacked silver dollars over the coil, I heard nothing but silence. QuickMask revealed that the signal was 1-28 - 1-30, which as you know the Andy S. coin program rejects.

I know that I'm 99.9999% unlikely to ever waive my coil over 2 stacked silver dollars, but my conscience is going to likely make me edit the Andy S. program "just in case." My common sense tells me that he is WAY more knowledgeable than me on the subject, and I should just leave it alone.

I've got less than a year on the e-trac and would love to hear some thoughts and opinions from the experts.

 

[cudamark]

You sure one of those "silver" dollars wasn't a fake?

 

[ArkieBassMan]

You sure one of those "silver" dollars wasn't a fake?

Reasonably sure. 1923-S Peace and 1889-P Morgan. Both belonged to my grandfather who died in the early 1970's. I don't think anyone would have faked either of these common date/average condition coins in the 1960's or earlier as there would have been no reason to. They look, weigh, and sound correct.

The Morgan comes in at 1-41. The Peace at 1-40. Stacked one on top of the other, anywhere from 1-30 to 1-35.

 

[cudamark]

That's strange. If anything, you would think they would read higher, not lower.