I recently bought this lock off eBay since I live in California and can't really detect for civil war stuff here :-). Anyways, I can't figure out who the manufacturer is, any ideas?
The marking on your lock's brass keyhole-cover stands for Sargent & Company, of New Haven CT. It was founded in May 1864... and is still in business today. The form of your padlock (iron body with brass keyhole-cover marked S&Co.) indicates it is from the final 1/3rd of the 1800s into the early-1900s. You might find a match for it at an Antique Padlock collector's website, here: Smoke House Padlocks - S & Co - Antique Padlocks