That is a neat observation Terry, From what i am hearing,the numbers can register different in different areas of the country.
at least by a little.
Down here,Most but not all of the dimes come in at 12-45,12-46.
The last dime i dug was a seated,very deep,came in at 12-45 for me,i played and played with it before i dug.
one time i saw a 12-46 flash through the numbers,but that was the only time.
had a pretty good idea it was silver,and was hoping for a barber,never expected a seated.
They can come in at a lot of different numbers,i remember one i dug that read 11-39,but was a very worn and very thin
barber.
I am sure the differences have to do with different mineralization in different parts of the country.
I also agree with Terry on the dig by sound theory,I have found silver this way also.
Silver mixed in trash will read no telling where sometimes,but you will get the unmistakeable silver pitch in there too.
Learning is by digging,i learned that the hard way.
Best of luck to all and stay cool.
LabradorBob