Possible Civil War Era Padlock

Found this while rummaging through some old stuff. Unique in that the loop or clasp doesn't rotate but comes completely out. Doing some research someone claimed it was a padlock for a prison or slave shackle. Would like to learn more about it. I noticed that other padlocks had unique dot patterns and I assume that it was to identify the lock and matching key. Dates range from 1840s to 1860s.