The ironic thing is that some of the most valuable coins are NOT the high value, low mintage coins of the 19th century, they are the high mintage, low value coins.
There is a logical reason for this, and this is where the real metal detecting opportunity lies. Cents and lower value coins were widely used for commerce, therefore they were more likely to get lost than higher value coins.
Silver Dollars and Half Dollars were generally not popular coins with the general public. Many people in the 1800's never even owned more than a few Silver Dollars, and most never even saw one, let alone possess one. They were typically used for commerce by large corporations and banks. As coin collecting became popular during the early 20th century, there were millions of Silver & Half Dollar coins available to collectors in uncirculated condition. As late as the 1970's hundreds of thousands of Morgan Dollars were discovered by the US Treasury Department in uncirculated condition and released to the public.
Half Cents, Large Cents, 5 Cent Pieces, Half Dimes, and Dimes were used for everyday spending and either got worn out or lost, or hidden in caches, and therefore command a premium to collectors. Half Cents are extremely rare. These are the coins most sought after by collectors and these are the coins we are most likely to find while metal detecting.